Critics of applying conventional quantitative research methods to the problems of social work practice research have ignored the considerable progress which has been achieved during the past decade in scientifically documenting the effectiveness of social services. A set of First Principles of Practice Research is outlined for use by researchers in the design and conduct of practice research, and for use by the consumers of research to evaluate the methodological rigour of practice experiments. The advocates of qualitative research are urged to provide the profession with similar positive examples of research on the outcomes of social work practice, and to develop explicit guide-lines for the conduct of qualitative studies.