It is becoming increasingly important to facilitate the integrated management of user information. Exchanging user information across heterogeneous systems has many benefits, particularly in enhancing the quality and quantity of user information available for personalization. One common approach to user model interoperability is the use of mapping tools to manually build rich executable mappings between user models. A key problem with existing approaches is that the mapping tools are often too generic for these specialized tasks and do not provide any support to an administrator mapping in a specific domain such as user models. This paper presents a novel approach to user model interoperability which lowers the complexity and provides support to administrators in completing user model mappings. The domain-aware approach to user model interoperability incorporates interchangeable domain knowledge directly into the integration tools. This approach was implemented in a system called FUMES which is a mapping creation and execution environment that includes two domain-aware mechanisms; a canonical user model and user model mapping types. FUMES was deployed in an integration of existing user models and the domain-aware approach was then evaluated in a user study. The evaluation consisted of a direct comparison with a generic approach to user model interoperability which was applied using the commercial mapping tool, Altova Mapforce. The results of this evaluation demonstrate improvements in mapping accuracy and usability when using the domain-aware approach compared to the generic mapping approach.