Abstract-- In ubiquitous computing environments, many devices and agents interoperate with each other and use services provided by others. But the problem is that there may be requests that can not be fulfilled by available services. A solution to this problem is to use service brokers that compose existing services and create new value added services that can fulfill the clients' requests. In this paper, we present an architecture for a contextaware service broker that not only is able to compose services for responding to new requests, but also considers the context of its clients for providing customized and personalized outputs and behaviors.