This article elucidates criteria which might be helpful in evaluating praxis-related research. The authors explore both sides of the research and development (R & D) project. They examine different ways of understanding contributions to knowledge through research but more especially exploring ideas about contributions to changing praxis. Changing praxis necessarily involves changing not only each participant as an individual actor, but changing patterns of activity. In most praxis-related research, this is pursued by involving a widening range of participants in a setting. This poses the further problem that the ripple effects of the project are not entirely under the researcher's control. Thus, as the title suggests, praxis-related research serves two masters. Very often, R & D projects aim to make contributions to social science. Generally they also aim to make contributions to the world of human affairs. Different criteria are appropriate for judging each. (Contains 1 figure.)