In this article we present an approach to the development of software systems supporting electronic commerce. The basic idea of this approach is to develop systems of this kind, called electronic commerce applications (ECAs), following a process-oriented approach. That means, at first we model the processes to be supported by an ECA.Our emphasis is on the specification of the communication interfaces between process parts which take place at different sites. In a second step we use these specifications to simulate the behavior of distributed processes and to implement the software needed for the support of the specified ECA.