Use of shared electronic health records opens a whole range of new possibilities for flexible and fruitful cooperation among health personnel in different health institutions, to the benefit of the patients. There are, however, unsolved legal and security challenges. The overall aim of this article is to highlight legal and security challenges that should be considered before using shared electronic cooperation platforms and health record systems to avoid legal and security "surprises" subsequent to the implementation. Practical lessons learned from the use of a web-based ulcer record system involving patients, community nurses, GPs, and hospital nurses and doctors in specialist health care are used to illustrate challenges we faced. Discussion of possible legal and security challenges is critical for successful implementation of shared electronic collaboration systems. Key challenges include (1) allocation of responsibility, (2) documentation routines, (3) and integrated or federated access control. We discuss and suggest how challenges of legal and security aspects can be handled. This discussion may be useful for both current and future users, as well as policy makers.