The study evaluates the effectiveness of an in-service science program through measuring the use of materials available from the school district's resource supply center. This in-service program introduced the Science Curriculum Improvement Study simultaneously into all 35 elementary schools of one district. The live-material shipment orders served as an unobtrusive means of measuring teachers' behaviors. The 168 participants in the workshop before implementation did not significantly differ from the other 361 teachers in their use of materials. These participants were selected on the basis of availability and representation from each school. On a questionnaire they indicated a very high level of satisfaction with the workshop. The 128 participants in a second workshop during the summer following the first year of implementation made significantly greater use of the materials.