diff --git a/Makefile.am b/Makefile.am
index c5392415..e73f8884 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -704,7 +704,8 @@ doc_files = doc/overview.txt doc/ofono-paper.txt doc/release-faq.txt \
 			doc/networkmonitor-api.txt \
 			doc/allowed-apns-api.txt \
 			doc/lte-api.txt \
-			doc/cinterion-hardware-monitor-api.txt
+			doc/cinterion-hardware-monitor-api.txt \
+			doc/ims-api.txt
 
 
 test_scripts = test/backtrace \
diff --git a/doc/ims-api.txt b/doc/ims-api.txt
new file mode 100644
index 00000000..c4f5ffad
--- /dev/null
+++ b/doc/ims-api.txt
@@ -0,0 +1,59 @@
+IpMultimediaSystem Hierarchy
+============================
+
+Service		org.ofono
+Interface	org.ofono.IpMultimediaSystem
+Object path	[variable prefix]/{modem0,modem1,...}
+
+Methods		dict GetProperties()
+
+			Returns all IpMultimediaSystem configuration properties.
+
+		void SetProperty(string property, variant value)
+
+			Changes the value of the specified property. Only
+			properties that are listed as readwrite are
+			changeable. On success a PropertyChanged signal
+			will be emitted.
+
+			Possible Errors: [service].Error.InProgress
+					 [service].Error.InvalidArguments
+					 [service].Error.Failed
+
+		void Register()
+
+			Attempts to register to IMS. A successful method return
+			indicates that the registration process could be
+			initiated successfully. The actual registration state
+			will be reflected by the 'Registered' property.
+
+			Possible Errors: [service].Error.InProgress
+					 [service].Error.NotImplemented
+
+		void Unregister()
+
+			Attempts to unregister from IMS. A successful method
+			return indicates that the unregistration process could
+			be initiated successfully. The actual unregistration
+			state will be reflected by the 'Registered' property.
+
+			Possible Errors: [service].Error.InProgress
+					 [service].Error.NotImplemented
+
+Signals		PropertyChanged(string property, variant value)
+
+			This signal indicates a changed value of the given
+			property.
+
+Properties	boolean Registered [readonly]
+
+			Contains the current IMS registration state.
+
+		boolean VoiceCapable [readonly, optional]
+
+			Boolean representing whether voice call transfer over
+			RTP (IMS) is available.
+
+		boolean SmsCapable [readonly, optional]
+
+			Boolean representing whether SMS-over-IMS is available.