We propose a technique for the automated synthesis of new comeb services. Given a set of abstract BPEL4WS descriptions of component services, and a composition requirement, we automatically generate a concrete BPEL4WS process that, when executed, interacts with the components and satisfies the requirement. We implement the proposed approach exploiting efficient representation techniques, and we show its scalability over case studies taken from a real world application and over a parameterized domain. Categories and Subject Descriptors: H.3.5 Online Information Services: Web-Based Services General Terms: Algorithms, Experimentation