In a small group of people it is quite easy to start a collaboration based on shared trust, because people quickly recognize quality of each other. But this is not true when we move to the highly distributed environment with hundreds of users, not only from one institution or town, but even from different countries. It becomes very complicated task to distinguish experienced an trusted people from malicious users. In the paper a reputation system proposed particularly for a medical environment supporting collaboration among physicians is presented. The system provides tools for sharing knowledge and expertize in form of modules which can be seamlessly connected to each other provided more advanced functionality. The reputation system is des...