The role of evaluation in a working model for the diffusion of educational innovations is the central topic of this paper. The working model is a product of the Trent Valley Centre (TVC), a "regional laboratory" type extension center of the Ontario Institute for Studies in Education. The first objective of the program is to generate the working model for the diffusion of educational innovations, both process and product, and the second objective is to implement the emerging model in a school system that is characterized by the absence of markedly atypical features. The major components of the model include: a climate for change; academic-practitioner interaction; roles for evaluation; program development strategies; interschool cooperation; county wide communication networks; and teacher responsibility for change. Stages in the model include: agreement to begin; establishment of an organization; selection of problems and goals; study of available solutions; pilot trials; adopt, adapt, reject decisions; and field trial. The major contribution to new knowledge that this model makes has to do with the ways in which the components interact to produce validated educational change. (Author/DB)