Innovative doctrines create dilemmas for teachers. These dilemmas arise because, when teachers decide to adopt new practices, they face new uncertainties about their role in the classroom, the effectiveness of their methods and the purposes of their instruction. The way teachers used the materials of a particular innovation, the Schools Council Integrated Science Project, is described and explained in terms of teacher control over the uncertainties of classroom life. The Project proposals, initially seen by teachers as increasing the diffuseness of their work, were modified by them so that it was clearer to them what was to be accomplished and how it was to be done. At the same time, a functional alignment of goals, techniques and socialrelationships was maintained through teacher influence in the classroom. The translation of the materials into more specific terms meant that important elements of the "doctrine" of the Project were either ignored or redefined in more traditional terms. Such redefinition of innovation in specific terms raises questions about the effectiveness, as instruments of change, of centralized curriculum projects remote from the practical problems of schools. Implications for curriculum policy and research into the dilemmas teachers face in teaching are discussed.