A composite web service often interacts with several partner web services hosted in different servers. These partner web services are represented as activities in a WS-BPEL program describing the composite web service. Invoking the maximal number of these activities concurrently is essential for improving its performance. But complex message coupling and control dependency between activities in a composite web service may prevent them from being arranged correctly and efficiently. In this paper, we propose an approach for detecting problematic activity arrangement in a WS-BPEL program based on analyzing message propagation and activity dependency in the program. The underlying idea of our approach is to check whether activities with dependency are arranged as concurrent and whether activities without dependency are arranged as sequential. Our preliminary empirical results demonstrate the effectiveness of our approach. © 2011 IEEE.