We consider the professional development of in-service teachers and review traditional development efforts that have been used in the past. An alternative form of professional development using Japanese lesson study is proposed and discussed as a possibility. A case study involving the Mpumalanga Secondary Science Initiative, where lesson study was used, is described and its efficacy reviewed. The project was aimed at improving mathematics and science learning of secondary school learners using lesson study for teacher development. The discussion concludes with a reflection on the outcomes and efforts of the project.