diff --git a/promql/ast.go b/promql/ast.go
index 09c6fd44d..bc19d76f1 100644
--- a/promql/ast.go
+++ b/promql/ast.go
@@ -104,6 +104,7 @@ type AggregateExpr struct {
 	Op              itemType         // The used aggregation operation.
 	Expr            Expr             // The vector expression over which is aggregated.
 	Grouping        model.LabelNames // The labels by which to group the vector.
+	Without         bool             // Whether to drop the given labels rather than keep them.
 	KeepExtraLabels bool             // Whether to keep extra labels common among result elements.
 }
 
diff --git a/promql/engine.go b/promql/engine.go
index c1cceb048..f52bbc71a 100644
--- a/promql/engine.go
+++ b/promql/engine.go
@@ -619,7 +619,7 @@ func (ev *evaluator) eval(expr Expr) model.Value {
 	switch e := expr.(type) {
 	case *AggregateExpr:
 		vector := ev.evalVector(e.Expr)
-		return ev.aggregation(e.Op, e.Grouping, e.KeepExtraLabels, vector)
+		return ev.aggregation(e.Op, e.Grouping, e.Without, e.KeepExtraLabels, vector)
 
 	case *BinaryExpr:
 		lhs := ev.evalOneOf(e.LHS, model.ValScalar, model.ValVector)
@@ -1039,12 +1039,25 @@ type groupedAggregation struct {
 }
 
 // aggregation evaluates an aggregation operation on a vector.
-func (ev *evaluator) aggregation(op itemType, grouping model.LabelNames, keepExtra bool, vec vector) vector {
+func (ev *evaluator) aggregation(op itemType, grouping model.LabelNames, without bool, keepExtra bool, vec vector) vector {
 
 	result := map[uint64]*groupedAggregation{}
 
 	for _, sample := range vec {
-		groupingKey := model.SignatureForLabels(sample.Metric.Metric, grouping...)
+		withoutMetric := sample.Metric
+		if without {
+			for _, l := range grouping {
+				withoutMetric.Del(l)
+			}
+			withoutMetric.Del(model.MetricNameLabel)
+		}
+
+		var groupingKey uint64
+		if without {
+			groupingKey = uint64(withoutMetric.Metric.Fingerprint())
+		} else {
+			groupingKey = model.SignatureForLabels(sample.Metric.Metric, grouping...)
+		}
 
 		groupedResult, ok := result[groupingKey]
 		// Add a new group if it doesn't exist.
@@ -1053,6 +1066,8 @@ func (ev *evaluator) aggregation(op itemType, grouping model.LabelNames, keepExt
 			if keepExtra {
 				m = sample.Metric
 				m.Del(model.MetricNameLabel)
+			} else if without {
+				m = withoutMetric
 			} else {
 				m = metric.Metric{
 					Metric: model.Metric{},
diff --git a/promql/lex.go b/promql/lex.go
index 7817d3421..90f82f373 100644
--- a/promql/lex.go
+++ b/promql/lex.go
@@ -158,6 +158,7 @@ const (
 	itemKeepCommon
 	itemOffset
 	itemBy
+	itemWithout
 	itemOn
 	itemGroupLeft
 	itemGroupRight
@@ -192,6 +193,7 @@ var key = map[string]itemType{
 	"annotations":   itemAnnotations,
 	"offset":        itemOffset,
 	"by":            itemBy,
+	"without":       itemWithout,
 	"keeping_extra": itemKeepCommon,
 	"keep_common":   itemKeepCommon,
 	"on":            itemOn,
diff --git a/promql/lex_test.go b/promql/lex_test.go
index e3f0b4c4e..cb1642aec 100644
--- a/promql/lex_test.go
+++ b/promql/lex_test.go
@@ -261,6 +261,9 @@ var tests = []struct {
 	}, {
 		input:    "by",
 		expected: []item{{itemBy, 0, "by"}},
+	}, {
+		input:    "without",
+		expected: []item{{itemWithout, 0, "without"}},
 	}, {
 		input:    "on",
 		expected: []item{{itemOn, 0, "on"}},
diff --git a/promql/parse.go b/promql/parse.go
index a23986973..5912809bc 100644
--- a/promql/parse.go
+++ b/promql/parse.go
@@ -732,11 +732,14 @@ func (p *parser) aggrExpr() *AggregateExpr {
 		p.errorf("expected aggregation operator but got %s", agop)
 	}
 	var grouping model.LabelNames
-	var keepExtra bool
+	var keepExtra, without bool
 
 	modifiersFirst := false
 
-	if p.peek().typ == itemBy {
+	if t := p.peek().typ; t == itemBy || t == itemWithout {
+		if t == itemWithout {
+			without = true
+		}
 		p.next()
 		grouping = p.labels()
 		modifiersFirst = true
@@ -752,10 +755,13 @@ func (p *parser) aggrExpr() *AggregateExpr {
 	p.expect(itemRightParen, ctx)
 
 	if !modifiersFirst {
-		if p.peek().typ == itemBy {
+		if t := p.peek().typ; t == itemBy || t == itemWithout {
 			if len(grouping) > 0 {
 				p.errorf("aggregation must only contain one grouping clause")
 			}
+			if t == itemWithout {
+				without = true
+			}
 			p.next()
 			grouping = p.labels()
 		}
@@ -765,10 +771,15 @@ func (p *parser) aggrExpr() *AggregateExpr {
 		}
 	}
 
+	if keepExtra && without {
+		p.errorf("cannot use 'keep_common' with 'without'")
+	}
+
 	return &AggregateExpr{
 		Op:              agop.typ,
 		Expr:            e,
 		Grouping:        grouping,
+		Without:         without,
 		KeepExtraLabels: keepExtra,
 	}
 }
diff --git a/promql/parse_test.go b/promql/parse_test.go
index 21744f6d2..07e5ce0c0 100644
--- a/promql/parse_test.go
+++ b/promql/parse_test.go
@@ -869,6 +869,32 @@ var testExpr = []struct {
 			},
 			Grouping: model.LabelNames{"foo"},
 		},
+	}, {
+		input: "sum without (foo) (some_metric)",
+		expected: &AggregateExpr{
+			Op:      itemSum,
+			Without: true,
+			Expr: &VectorSelector{
+				Name: "some_metric",
+				LabelMatchers: metric.LabelMatchers{
+					{Type: metric.Equal, Name: model.MetricNameLabel, Value: "some_metric"},
+				},
+			},
+			Grouping: model.LabelNames{"foo"},
+		},
+	}, {
+		input: "sum (some_metric) without (foo)",
+		expected: &AggregateExpr{
+			Op:      itemSum,
+			Without: true,
+			Expr: &VectorSelector{
+				Name: "some_metric",
+				LabelMatchers: metric.LabelMatchers{
+					{Type: metric.Equal, Name: model.MetricNameLabel, Value: "some_metric"},
+				},
+			},
+			Grouping: model.LabelNames{"foo"},
+		},
 	}, {
 		input: "stddev(some_metric)",
 		expected: &AggregateExpr{
@@ -920,6 +946,18 @@ var testExpr = []struct {
 		input:  "MIN by(test) (some_metric) keep_common",
 		fail:   true,
 		errMsg: "could not parse remaining input \"keep_common\"...",
+	}, {
+		input:  `sum (some_metric) without (test) keep_common`,
+		fail:   true,
+		errMsg: "cannot use 'keep_common' with 'without'",
+	}, {
+		input:  `sum (some_metric) without (test) by (test)`,
+		fail:   true,
+		errMsg: "could not parse remaining input \"by (test)\"...",
+	}, {
+		input:  `sum without (test) (some_metric) by (test)`,
+		fail:   true,
+		errMsg: "could not parse remaining input \"by (test)\"...",
 	},
 	// Test function calls.
 	{
diff --git a/promql/printer.go b/promql/printer.go
index 7be0de04e..e35699d7d 100644
--- a/promql/printer.go
+++ b/promql/printer.go
@@ -137,7 +137,12 @@ func (es Expressions) String() (s string) {
 func (node *AggregateExpr) String() string {
 	aggrString := fmt.Sprintf("%s(%s)", node.Op, node.Expr)
 	if len(node.Grouping) > 0 {
-		format := "%s BY (%s)"
+		var format string
+		if node.Without {
+			format = "%s WITHOUT (%s)"
+		} else {
+			format = "%s BY (%s)"
+		}
 		if node.KeepExtraLabels {
 			format += " KEEP_COMMON"
 		}
diff --git a/promql/printer_test.go b/promql/printer_test.go
index 473305b61..890adc661 100644
--- a/promql/printer_test.go
+++ b/promql/printer_test.go
@@ -30,6 +30,9 @@ func TestExprString(t *testing.T) {
 		{
 			in: `sum(task:errors:rate10s{job="s"}) BY (code) KEEP_COMMON`,
 		},
+		{
+			in: `sum(task:errors:rate10s{job="s"}) WITHOUT (instance)`,
+		},
 		{
 			in: `up > BOOL 0`,
 		},
diff --git a/promql/testdata/aggregators.test b/promql/testdata/aggregators.test
new file mode 100644
index 000000000..de4dd1e83
--- /dev/null
+++ b/promql/testdata/aggregators.test
@@ -0,0 +1,115 @@
+load 5m
+  http_requests{job="api-server", instance="0", group="production"} 0+10x10
+  http_requests{job="api-server", instance="1", group="production"} 0+20x10
+  http_requests{job="api-server", instance="0", group="canary"}   0+30x10
+  http_requests{job="api-server", instance="1", group="canary"}   0+40x10
+  http_requests{job="app-server", instance="0", group="production"} 0+50x10
+  http_requests{job="app-server", instance="1", group="production"} 0+60x10
+  http_requests{job="app-server", instance="0", group="canary"}   0+70x10
+  http_requests{job="app-server", instance="1", group="canary"}   0+80x10
+
+load 5m
+  foo{job="api-server", instance="0", region="europe"} 0+90x10
+  foo{job="api-server"} 0+100x10
+
+# Simple sum.
+eval instant at 50m SUM BY (group) (http_requests{job="api-server"})
+  {group="canary"} 700
+  {group="production"} 300
+
+# Test alternative "by"-clause order.
+eval instant at 50m sum by (group) (http_requests{job="api-server"})
+  {group="canary"} 700
+  {group="production"} 300
+
+# Simple average.
+eval instant at 50m avg by (group) (http_requests{job="api-server"})
+  {group="canary"} 350
+  {group="production"} 150
+
+# Simple count.
+eval instant at 50m count by (group) (http_requests{job="api-server"})
+  {group="canary"} 2
+  {group="production"} 2
+
+# Simple without.
+eval instant at 50m sum without (instance) (http_requests{job="api-server"})
+  {group="canary",job="api-server"} 700
+  {group="production",job="api-server"} 300
+
+# Without with mismatched and missing labels. Do not do this.
+eval instant at 50m sum without (instance) (http_requests{job="api-server"} or foo)
+  {group="canary",job="api-server"} 700
+  {group="production",job="api-server"} 300
+  {region="europe",job="api-server"} 900
+  {job="api-server"} 1000
+
+# Lower-cased aggregation operators should work too.
+eval instant at 50m sum(http_requests) by (job) + min(http_requests) by (job) + max(http_requests) by (job) + avg(http_requests) by (job)
+  {job="app-server"} 4550
+  {job="api-server"} 1750
+
+# Test alternative "by"-clause order with "keep_common".
+eval instant at 50m sum by (group) keep_common (http_requests{job="api-server"})
+  {group="canary", job="api-server"} 700
+  {group="production", job="api-server"} 300
+
+# Test both alternative "by"-clause orders in one expression.
+# Public health warning: stick to one form within an expression (or even
+# in an organization), or risk serious user confusion.
+eval instant at 50m sum(sum by (group) keep_common (http_requests{job="api-server"})) by (job)
+  {job="api-server"} 1000
+
+
+
+# Standard deviation and variance.
+eval instant at 50m stddev(http_requests)
+  {} 229.12878474779
+
+eval instant at 50m stddev by (instance)(http_requests)
+  {instance="0"} 223.60679774998
+  {instance="1"} 223.60679774998
+
+eval instant at 50m stdvar(http_requests)
+  {} 52500
+
+eval instant at 50m stdvar by (instance)(http_requests)
+  {instance="0"} 50000
+  {instance="1"} 50000
+
+
+
+# Regression test for missing separator byte in labelsToGroupingKey.
+clear
+load 5m
+  label_grouping_test{a="aa", b="bb"} 0+10x10
+  label_grouping_test{a="a", b="abb"} 0+20x10
+
+eval instant at 50m sum(label_grouping_test) by (a, b)
+  {a="a", b="abb"} 200
+  {a="aa", b="bb"} 100
+
+
+
+# Tests for min/max.
+clear
+load 5m
+  http_requests{job="api-server", instance="0", group="production"}	1
+  http_requests{job="api-server", instance="1", group="production"}	2
+  http_requests{job="api-server", instance="0", group="canary"}		NaN
+  http_requests{job="api-server", instance="1", group="canary"}		3
+  http_requests{job="api-server", instance="2", group="canary"}		4
+
+eval instant at 0m max(http_requests)
+  {} 4
+
+eval instant at 0m min(http_requests)
+  {} 1
+
+eval instant at 0m max by (group) (http_requests)
+  {group="production"} 2
+  {group="canary"} 4
+
+eval instant at 0m min by (group) (http_requests)
+  {group="production"} 1
+  {group="canary"} 3
diff --git a/promql/testdata/legacy.test b/promql/testdata/legacy.test
index d80293f0f..c4c811107 100644
--- a/promql/testdata/legacy.test
+++ b/promql/testdata/legacy.test
@@ -147,12 +147,6 @@ eval instant at 50m x{y="testvalue"}
 	x{y="testvalue"} 100 
 
 
-# Lower-cased aggregation operators should work too.
-eval instant at 50m sum(http_requests) by (job) + min(http_requests) by (job) + max(http_requests) by (job) + avg(http_requests) by (job)
-	{job="app-server"} 4550 
-	{job="api-server"} 1750 
-
-
 # Deltas should be adjusted for target interval vs. samples under target interval.
 eval instant at 50m delta(http_requests{group="canary", instance="1", job="app-server"}[18m])
 	{group="canary", instance="1", job="app-server"} 288
@@ -343,22 +337,6 @@ eval instant at 50m {job=~".+-server", job!~"api-.+"}
 	http_requests{group="production", instance="0", job="app-server"} 500 
 	http_requests{group="production", instance="1", job="app-server"} 600 
 
-# Test alternative "by"-clause order.
-eval instant at 50m sum by (group) (http_requests{job="api-server"})
-	{group="canary"} 700 
-	{group="production"} 300 
-
-# Test alternative "by"-clause order with "keep_common".
-eval instant at 50m sum by (group) keep_common (http_requests{job="api-server"})
-	{group="canary", job="api-server"} 700 
-	{group="production", job="api-server"} 300 
-
-# Test both alternative "by"-clause orders in one expression.
-# Public health warning: stick to one form within an expression (or even
-# in an organization), or risk serious user confusion.
-eval instant at 50m sum(sum by (group) keep_common (http_requests{job="api-server"})) by (job)
-	{job="api-server"} 1000 
-
 eval instant at 50m http_requests{group="canary"} and http_requests{instance="0"}
 	http_requests{group="canary", instance="0", job="api-server"} 300 
 	http_requests{group="canary", instance="0", job="app-server"} 700 
@@ -487,11 +465,6 @@ eval instant at 50m rate(http_requests{group="production",job="api-server"}[10m]
 	{group="production", instance="0", job="api-server"} 0.03333333333333333 
 	{group="production", instance="1", job="api-server"} 0.06666666666666667 
 
-# Regression test for missing separator byte in labelsToGroupingKey.
-eval instant at 50m sum(label_grouping_test) by (a, b)
-	{a="a", b="abb"} 200 
-	{a="aa", b="bb"} 100 
-
 eval instant at 50m http_requests{group="canary", instance="0", job="api-server"} / 0
 	{group="canary", instance="0", job="api-server"} +Inf 
 
@@ -560,20 +533,6 @@ eval instant at 50m log10(vector_matching_a - 20)
 	{l="x"} NaN 
 	{l="y"} -Inf 
 
-eval instant at 50m stddev(http_requests)
-	{} 229.12878474779 
-
-eval instant at 50m stddev by (instance)(http_requests)
-	{instance="0"} 223.60679774998 
-	{instance="1"} 223.60679774998 
-
-eval instant at 50m stdvar(http_requests)
-	{} 52500 
-
-eval instant at 50m stdvar by (instance)(http_requests)
-	{instance="0"} 50000 
-	{instance="1"} 50000
-
 
 # Matrix tests.
 
diff --git a/promql/testdata/operators.test b/promql/testdata/operators.test
deleted file mode 100644
index fbef5030c..000000000
--- a/promql/testdata/operators.test
+++ /dev/null
@@ -1,22 +0,0 @@
-# Tests for min/max.
-clear
-load 5m
-  http_requests{job="api-server", instance="0", group="production"}	1
-  http_requests{job="api-server", instance="1", group="production"}	2
-  http_requests{job="api-server", instance="0", group="canary"}		NaN
-  http_requests{job="api-server", instance="1", group="canary"}		3
-  http_requests{job="api-server", instance="2", group="canary"}		4
-
-eval instant at 0m max(http_requests)
-  {} 4
-
-eval instant at 0m min(http_requests)
-  {} 1
-
-eval instant at 0m max by (group) (http_requests)
-  {group="production"} 2
-  {group="canary"} 4
-
-eval instant at 0m min by (group) (http_requests)
-  {group="production"} 1
-  {group="canary"} 3