Social requirements are defined as the users’ needs related to the use of an application in interaction with others. This paper aims to formulate social requirements of health 2.0 applications for professional healthcare workers. Collaboration is seen as the central characteristic of these applications. To detect the social requirements, we first identified four features that determine how healthcare professionals collaborate: (1) the professional status of healthcare professionals; (2) patient centeredness; (3) ambiguity in medicine and (4) complex organisation of healthcare. Based on these characteristics and findings of Computer-Supported Cooperative Work (CSCW) research in healthcare, we were able to formulate three social requirements for health 2.0 applications: (1) supported autonomy; (2) rationale in context; and (3) fluid collaboration. These requirements will serve as input for health 2.0 scenarios.