diff --git a/ChangeLog b/ChangeLog
index 615aaa41..3a54dbff 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2009-05-15  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
+
+	Added changeOption command. Currently, max-download-limit,
+	max-upload-limit option are available in this command.
+	* src/RequestGroup.h
+	* src/XmlRpcMethod.cc
+	* src/XmlRpcMethod.h
+	* src/XmlRpcMethodFactory.cc
+	* src/XmlRpcMethodImpl.cc
+	* src/XmlRpcMethodImpl.h
+	* test/XmlRpcMethodTest.cc
+
 2009-05-14  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
 
 	Added purgeDownloadResult command.
diff --git a/src/RequestGroup.h b/src/RequestGroup.h
index 02b7dd15..6deed1ab 100644
--- a/src/RequestGroup.h
+++ b/src/RequestGroup.h
@@ -473,10 +473,22 @@ public:
     return _maxDownloadSpeedLimit;
   }
 
+  void setMaxDownloadSpeedLimit(unsigned int speed)
+  {
+    _maxDownloadSpeedLimit = speed;
+  }
+
   unsigned int getMaxUploadSpeedLimit() const
   {
     return _maxUploadSpeedLimit;
   }
+
+  void setMaxUploadSpeedLimit(unsigned int speed)
+  {
+    _maxUploadSpeedLimit = speed;
+  }
+
+  static void resetGIDCounter() { _gidCounter = 0; }
 };
 
 typedef SharedHandle<RequestGroup> RequestGroupHandle;
diff --git a/src/XmlRpcMethod.cc b/src/XmlRpcMethod.cc
index 89a4579b..145dc9a1 100644
--- a/src/XmlRpcMethod.cc
+++ b/src/XmlRpcMethod.cc
@@ -74,16 +74,20 @@ XmlRpcResponse XmlRpcMethod::execute
   }
 }
 
-void XmlRpcMethod::gatherRequestOption
-(const SharedHandle<Option>& option, const BDE& optionsDict)
+
+template<typename InputIterator>
+static void gatherOption
+(InputIterator first, InputIterator last,
+ const SharedHandle<Option>& option, const BDE& optionsDict,
+ const SharedHandle<OptionParser>& optionParser)
 {
-  for(std::vector<std::string>::const_iterator i = listRequestOptions().begin();
-      i != listRequestOptions().end(); ++i) {
-    if(optionsDict.containsKey(*i)) {
-      const BDE& value = optionsDict[*i];
-      SharedHandle<OptionHandler> optionHandler = _optionParser->findByName(*i);
+  for(; first != last; ++first) {
+    if(optionsDict.containsKey(*first)) {
+      const BDE& value = optionsDict[*first];
+      SharedHandle<OptionHandler> optionHandler =
+	optionParser->findByName(*first);
       // header and index-out option can take array as value
-      if((*i == PREF_HEADER || *i == PREF_INDEX_OUT) && value.isList()) {
+      if((*first == PREF_HEADER || *first == PREF_INDEX_OUT) && value.isList()){
 	for(BDE::List::const_iterator argiter = value.listBegin();
 	    argiter != value.listEnd(); ++argiter) {
 	  if((*argiter).isString()) {
@@ -94,7 +98,32 @@ void XmlRpcMethod::gatherRequestOption
 	optionHandler->parse(*option.get(), value.s());
       }
     }
-  }
+  }  
+}
+
+void XmlRpcMethod::gatherRequestOption
+(const SharedHandle<Option>& option, const BDE& optionsDict)
+{
+  gatherOption(listRequestOptions().begin(), listRequestOptions().end(),
+	       option, optionsDict, _optionParser);
+}
+
+const std::vector<std::string>& listChangeableOptions()
+{
+  static const std::string OPTIONS[] = {
+    PREF_MAX_UPLOAD_LIMIT,
+    PREF_MAX_DOWNLOAD_LIMIT,
+  };
+  static std::vector<std::string> options
+    (&OPTIONS[0], &OPTIONS[arrayLength(OPTIONS)]);;
+  return options;
+}
+
+void XmlRpcMethod::gatherChangeableOption
+(const SharedHandle<Option>& option, const BDE& optionsDict)
+{
+  gatherOption(listChangeableOptions().begin(), listChangeableOptions().end(),
+	       option, optionsDict, _optionParser);
 }
 
 } // namespace xmlrpc
diff --git a/src/XmlRpcMethod.h b/src/XmlRpcMethod.h
index 9e7ad919..51f61723 100644
--- a/src/XmlRpcMethod.h
+++ b/src/XmlRpcMethod.h
@@ -64,6 +64,9 @@ protected:
 
   void gatherRequestOption(const SharedHandle<Option>& option,
 			   const BDE& optionsDict);
+
+  void gatherChangeableOption(const SharedHandle<Option>& option,
+			      const BDE& optionDict);
 public:
   XmlRpcMethod();
 
diff --git a/src/XmlRpcMethodFactory.cc b/src/XmlRpcMethodFactory.cc
index 280d47af..5b1de65c 100644
--- a/src/XmlRpcMethodFactory.cc
+++ b/src/XmlRpcMethodFactory.cc
@@ -62,6 +62,8 @@ XmlRpcMethodFactory::create(const std::string& methodName)
     return SharedHandle<XmlRpcMethod>(new GetPeersXmlRpcMethod());
   } else if(methodName == "aria2.tellActive") {
     return SharedHandle<XmlRpcMethod>(new TellActiveXmlRpcMethod());
+  } else if(methodName == "aria2.changeOption") {
+    return SharedHandle<XmlRpcMethod>(new ChangeOptionXmlRpcMethod());
   } else if(methodName == "aria2.purgeDownloadResult") {
     return SharedHandle<XmlRpcMethod>(new PurgeDownloadResultXmlRpcMethod());
   } else {
diff --git a/src/XmlRpcMethodImpl.cc b/src/XmlRpcMethodImpl.cc
index c542c1de..cb6ccfff 100644
--- a/src/XmlRpcMethodImpl.cc
+++ b/src/XmlRpcMethodImpl.cc
@@ -60,6 +60,7 @@
 #include "BtProgressInfoFile.h"
 #include "BtRuntime.h"
 #include "BtAnnounce.h"
+#include "prefs.h"
 
 namespace aria2 {
 
@@ -459,6 +460,34 @@ BDE PurgeDownloadResultXmlRpcMethod::process
   return BDE("OK");
 }
 
+BDE ChangeOptionXmlRpcMethod::process
+(const XmlRpcRequest& req, DownloadEngine* e)
+{
+  const BDE& params = req._params;
+  assert(params.isList());
+  if(params.empty() || !params[0].isString()) {
+    throw DlAbortEx("GID is not provided.");
+  }  
+  int32_t gid = Util::parseInt(params[0].s());
+
+  SharedHandle<RequestGroup> group = findRequestGroup(e->_requestGroupMan, gid);
+  if(group.isNull()) {
+    throw DlAbortEx
+      (StringFormat("Cannot change option for GID#%d", gid).str());
+  }
+  SharedHandle<Option> option(new Option(*group->getOption().get()));
+  if(params.size() > 1 && params[1].isDict()) {
+    gatherChangeableOption(option, params[1]);
+  }
+  if(option->defined(PREF_MAX_DOWNLOAD_LIMIT)) {
+    group->setMaxDownloadSpeedLimit(option->getAsInt(PREF_MAX_DOWNLOAD_LIMIT));
+  }
+  if(option->defined(PREF_MAX_UPLOAD_LIMIT)) {
+    group->setMaxUploadSpeedLimit(option->getAsInt(PREF_MAX_UPLOAD_LIMIT));
+  }
+  return BDE("OK");
+}
+
 BDE NoSuchMethodXmlRpcMethod::process
 (const XmlRpcRequest& req, DownloadEngine* e)
 {
diff --git a/src/XmlRpcMethodImpl.h b/src/XmlRpcMethodImpl.h
index 142cb2c7..6d25b390 100644
--- a/src/XmlRpcMethodImpl.h
+++ b/src/XmlRpcMethodImpl.h
@@ -91,6 +91,11 @@ protected:
   virtual BDE process(const XmlRpcRequest& req, DownloadEngine* e);
 };
 
+class ChangeOptionXmlRpcMethod:public XmlRpcMethod {
+protected:
+  virtual BDE process(const XmlRpcRequest& req, DownloadEngine* e);
+};
+
 class NoSuchMethodXmlRpcMethod:public XmlRpcMethod {
 protected:
   virtual BDE process(const XmlRpcRequest& req, DownloadEngine* e);
diff --git a/test/XmlRpcMethodTest.cc b/test/XmlRpcMethodTest.cc
index 59689a9d..171294a4 100644
--- a/test/XmlRpcMethodTest.cc
+++ b/test/XmlRpcMethodTest.cc
@@ -14,6 +14,7 @@
 #include "OptionHandler.h"
 #include "XmlRpcRequest.h"
 #include "XmlRpcResponse.h"
+#include "prefs.h"
 
 namespace aria2 {
 
@@ -23,6 +24,7 @@ class XmlRpcMethodTest:public CppUnit::TestFixture {
 
   CPPUNIT_TEST_SUITE(XmlRpcMethodTest);
   CPPUNIT_TEST(testAddUri);
+  CPPUNIT_TEST(testChangeOption);
   CPPUNIT_TEST(testNoSuchMethod);
   CPPUNIT_TEST_SUITE_END();
 private:
@@ -31,6 +33,7 @@ private:
 public:
   void setUp()
   {
+    RequestGroup::resetGIDCounter();
     _option.reset(new Option());
     _e.reset(new DownloadEngine(SharedHandle<EventPoll>(new SelectEventPoll())));
     _e->option = _option.get();
@@ -42,6 +45,7 @@ public:
   void tearDown() {}
 
   void testAddUri();
+  void testChangeOption();
   void testNoSuchMethod();
 };
 
@@ -63,6 +67,27 @@ void XmlRpcMethodTest::testAddUri()
 		       rgs.front()->getRemainingUris().front());
 }
 
+void XmlRpcMethodTest::testChangeOption()
+{
+  SharedHandle<RequestGroup> group
+    (new RequestGroup(_option, std::deque<std::string>()));
+  _e->_requestGroupMan->addReservedGroup(group);
+
+  ChangeOptionXmlRpcMethod m;
+  XmlRpcRequest req("aria2.changeOption", BDE::list());
+  req._params << BDE("1");
+  BDE opt = BDE::dict();
+  opt[PREF_MAX_DOWNLOAD_LIMIT] = BDE("100K");
+  opt[PREF_MAX_UPLOAD_LIMIT] = BDE("50K");
+  req._params << opt;
+  XmlRpcResponse res = m.execute(req, _e.get());
+
+  CPPUNIT_ASSERT_EQUAL(0, res._code);
+  CPPUNIT_ASSERT_EQUAL((unsigned int)100*1024,
+		       group->getMaxDownloadSpeedLimit());
+  CPPUNIT_ASSERT_EQUAL((unsigned int)50*1024, group->getMaxUploadSpeedLimit());
+}
+
 void XmlRpcMethodTest::testNoSuchMethod()
 {
   NoSuchMethodXmlRpcMethod m;