Many more teachers begin studying for masters' level awards than complete them. This situation is a concern to participants, providers and funders of courses. The research project reported here explores teachers' perceptions of factors affecting their success in completing assessed work. Questionnaire and interview responses from 46 students in three higher education institutions (HEIs) emphasise a number of motivational and inhibiting factors experienced by teachers. Some of these, including styles of assessment and access to resources, can be influenced positively by HEIs through course design and structures of institutional support. Other influential factors included time, personal circumstances and support in the workplace. Although these factors are not controlled by HEIs, they might be influenced by partnerships between tutors, school managers and local advisory staff working together to plan participation from course design to final impact. The research, although small-scale and exploratory, will thus be of interest to HEIs and their local and national partners who seek to increase participation, retention and completion rates of teachers engaged in Postgraduate Professional Development. (Contains 7 tables.)