This paper focuses on the process of designing and implementing a community platform for cancer patients with the objective to derive a process model for community engineering. Following an introduction to the situation of cancer patients in Germany we summarize our findings on cancer patients’ demands for trustworthy information as well as their need for interaction with peers in similar situations. On this basis we describe the process of translating socio-technical needs into system requirements and the steps undertaken to develop a functioning community platform for cancer patients. We combine a generic iterative process model for systems’ development with elements of prototyping towards an engineering process model for community platforms for cancer patients. The paper focuses on specialised situations and challenges concerning user interface development and system requirements’ analysis taken into account during system development.