This paper aims to demonstrate the value of participatory action research (PAR) for advancing scientific knowledge as well as for solving practical problems. The article supports the argument through brief summaries of three PAR cases in industry: Norwegian shipping, Xerox Corporation, and the FAGOR group of the Mondragón cooperatives. While noting the practical gains achieved through PAR, the author concentrates particularly on the advances in substantive knowledge and theory that would have been unlikely to emerge out of more orthodox sociological research. The author suggests finally that wider use of participatory action research can have a stimulating effect upon the future development of sociology.