The authors ask whether and how action research can apply to health services research, given action research's claim to be radically different from mainstream research. They analyze the key tenets of an idealized version of action research, comparing them with those of the approach characteristic of mainstream research. The authors conclude, firstly, that action research deserves all credit for pioneering flexible and imaginative ways of working. Yet, there is nothing in the fundamental logic of the mainstream approach to preclude it from adopting some of these. Action researchers therefore need to reconsider their critical stance toward mainstream research. Conversely, mainstream researchers need to reconsider their critical stance toward the ways of working pioneered by action research and to adopt them as appropriate.