In this paper we present an approach for modelling and analyzing time-related properties of Web service compositions defined as a set of BPEL4WS processes. We introduce a formalism, called Web Service Timed State Transition Systems (WSTTS), to capture the timed behavior of the composite web services. We also exploit an interval temporal logic to express complex timed assumptions and requirements on the system?s behavior. Building upon of this formalization, we provide techniques and tools for model checking BPEL4WS compositions against time-related requirements. We perform a preliminary experimental evaluation of our approach and tools with the help of the e- Government case study.