diff --git a/CHANGELOG b/CHANGELOG
index 3f75343172..9205b897e2 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,4 @@
+* Add index to one2many's on_change
 * Remove auto-refresh on Action Window
 * Add support of domain for non-relation field
 * Manage microseconds in JSON-RPC and XML-RPC
diff --git a/doc/ref/models/fields.rst b/doc/ref/models/fields.rst
index 8316415a5b..63ae802fc7 100644
--- a/doc/ref/models/fields.rst
+++ b/doc/ref/models/fields.rst
@@ -66,6 +66,8 @@ with the values of the record.
 
 If true, the content of the field will be indexed.
 
+.. _ref-models-fields-on_change:
+
 ``on_change``
 -------------
 
diff --git a/doc/topics/index.rst b/doc/topics/index.rst
index ad1fcaec65..bae4107169 100644
--- a/doc/topics/index.rst
+++ b/doc/topics/index.rst
@@ -12,6 +12,7 @@ Introduction to all the key parts of trytond:
     install
     models/index
     models/fields_default_value
+    models/fields_on_change
     domain
     pyson
     actions
diff --git a/doc/topics/models/fields_on_change.rst b/doc/topics/models/fields_on_change.rst
new file mode 100644
index 0000000000..e47c787055
--- /dev/null
+++ b/doc/topics/models/fields_on_change.rst
@@ -0,0 +1,65 @@
+.. _topcis-fields_on_change:
+
+===================
+on_change of fields
+===================
+
+Tryton allows developers to define methods that can be called once a field's
+value has changed by the user this is the :ref:`ref-models-fields-on_change`
+method.  The method has the following name::
+
+    Model.on_change_<field name>
+
+This is an instance method, an instance of ``Model`` will be created by
+using the values from the form's fields specified by the ``on_change`` list
+defined on the field.
+
+There is also a way to define a method that must update a field whenever any
+field from a predefined list is modified. This list is defined by the
+:ref:`ref-models-fields-on_change_with` attribute of the field. The method
+that will be called has the following name::
+
+    Model.on_change_with_<field_name>
+
+Just like for the classic ``on_change``, an instance of ``Model`` will be
+created by using the values entered in the form's fields specified by the
+``on_change_with`` attribute.
+
+on_change & on_change_with return values
+----------------------------------------
+
+The return value of the method called will depend of the type of the call that
+occured. In case of an ``on_change`` the returned value will be a dictionary
+whose keys are field names to be modified and whose values will be the
+corresponding new value. In case of an ``on_change_with`` the returned value
+will be the new value of the field.
+
+Pay attention that the new value of a field differs according to its type.
+Simple fields require the value to be of the same type as the field.
+
+Relation fields require some more explanations:
+
+    - a ``field.One2Many`` or a ``field.Many2Many`` will accept either:
+
+        - a list of ``id`` denoting the new value that will replace all
+          previously ids.
+
+        - a dictionary composed of three keys: ``update``, ``add`` and
+          ``remove``.
+
+          The ``update`` key has as value a list of dictionary that denotes the
+          new value of the target's fields. The lines affected by the change
+          are found using the ``id`` key of the dictionary.
+
+          The ``add`` key have as value a list of tuple, the first element is
+          the index where a new line should be added, the second element is a
+          dictionary using the same convention as the dictionaries for the
+          ``update`` key.
+
+          The ``remove`` key will have as value a list of ids that will be
+          remove from the field.
+
+          Records that are not yet saved receive temporary ids (negative
+          integers) that can be used in with ``update`` or ``remove`` to
+          interact with them.
+