A comparative review of the research literature regarding the effectiveness of continuing professional development (CPD) demonstrates that a range of different factors needs to be present if it is to have impact in the classroom and that short CPD episodes are unlikely to be effective. The Earth Science Education Unit approach to CPD had to be through short-duration workshops as science teachers were unwilling to undertake prolonged CPD in this relatively minor component of the science curriculum. Follow-up research on the Earth Science Education Unit approach, using a variant of the framework developed by Guskey, showed that all of the schools that responded had changed their practice, with changes ranging from significant to modest. Meanwhile, self-reporting evidence showed a highly positive response with increases in knowledge and understanding. The results of the evaluation suggest that short-duration, well-structured CPD episodes, based on practical and interactive science teaching ideas, presented to whole science departments by experienced presenters, can have long-term impact on those involved. (Contains 6 tables.)