Considerable theoretical claims have been made for self-directed classroom-based research as a means for teacher and school development. There are relatively few empirical studies of the effects on teachers of doing this type of research. More are needed though the author stresses the need for effects to be approached in contextual and personal terms. This article reports on two such studies: one the evaluation of a higher-degree scheme for English state school teachers in which case study, evaluation and action research enquiries were done for students' theses; the other a collaborative action research project by the staff of one school. The effects on participating teachers are reported and commented upon, and tentative generalisations proposed.