On the one hand Web services are gaining increasing attention. A lot of standardization has improved their stability and range of application. Composition and coordination techniques for Web services enable an application integration effort beyond loosely coupled systems. On the other hand medical e-services are covered by the DICOM and HL7 communication protocols and profiled by the IHE (Integrating the Healthcare Enterprise) technical framework. Standardization is more extensive, most workflows are well defined and integration is tighter than in most other domains. Nevertheless standardization focused on conventional workflow systems. In an Internetbased medical environment with high security standards, communication is strongly restricted and conventional systems fail to deliver. This paper proposes a modeling process for medical Web services. The IHE patient administration process flow serves as a well defined example. Furthermore, the paper defines requirements of a Web service ba...