The way in which science teachers use innovation and the implications for curriculum policy making are addressed in five articles. In "Classroom Knowledge and Curriculum Change: An Introduction," John Olson proposes a humanistic framework for curricular change. Rob Walker's "The School, the Community, and the Outsider: Case Study of a Case Study," reflects on the nature of his work for the Case Studies in Science Education project and the advantages and limitations of the case method. In "The Programme, the Plans and the Activities of the Classroom: The Demands of Activity-Based Science," Edward L. Smith and Neil B. Sendelbach examine the antecedents of teacher classroom activity, including teachers' plans and the recommendations of teacher guides for the Science Curriculum Improvement Study programme. "Costs and Rewards of Innovation: Taking Account of the Teachers' Viewpoint," by Sally Brown and Donald McIntyre, considers the advantages and disadvantages of innovation, based on interviews with Scottish science teachers who were asked to implement the Scottish Integrated Science scheme. Finally, in "Dilemmas of Inquiry Teaching: How Teachers Cope," John Olson examines the concept of teachers' classroom influence as it is involved in change: implementation of the Schools Council Integrated Science Project. (SW)