The study traces changes in teachers’ views of in-service education during the first three years of the Development Program initiated by the Schools Commission in 1974. It also examines the impact of in-service in relation to other factors influencing change and professional development. The findings are discussed in relation to the recent National Inquiry into Teacher Education, the Auchmuty Report, which recommends an increase in the amount of in-service education available to teachers, particularly that which tertiary institutions might provide through a formal, credentialized system of medium-term courses. It is argued that the evidence of the survey points to the importance of strengthening, instead, informal systems of in-service education provision which enable teachers to help and learn from each other.