Reported here is one part of the nationally representative, "Schools and Continuing Professional Development in England--State of the Nation" research study which was funded by the Training and Development Agency for Schools (TDA). This paper sets out to understand how teachers and school leaders in England perceive the benefits and effectiveness of CPD activity. The investigation of benefits and effectiveness of CPD presented in the paper focuses on the various impacts that could result from participation, the forms and features of activities, as well as the conditions that make effectiveness more or less likely to occur. (Contains 9 tables.)