This study presents a typology of continuing professional development (CPD) activities and provides a discussion related to each. The typology includes 2 main themes, which investigate the various types of activities and the content presented in CPD programmes. The study used qualitative methods (open-ended questionnaires in addition to semi-structured interviews) with Saudi Arabian science teachers. The main theoretical framework for this study centres on the socio-constructivist theory of learning. Discussion of the findings leads to a depiction of what science teachers "need" to learn and "how" they want to learn. The aim of this study is to provide a framework for socio-constructivist science teacher professional development based on an attempt to understand how teachers learn effectively in CPD programmes and what science teachers need to learn.