A description and evaluation of a year-long science in-service program for elementary teachers is provided. Consisting of three components, the program was designed to expand teachers' understandings of physics and chemistry concepts and processes and to encourage more science teaching and science activities in their classrooms. The on-campus instructional components involved 90 hours of content instruction, laboratory activities, and acquisition of school district resource information and materials. Two-thirds of this time was devoted to traditional physics and chemistry topics and one-third to interdisciplinary topics such as solar energy, ecology, and science as a human activity. A sample lesson plan for physics and one for chemistry are provided. An off-campus in-service program conducted simultaneously with the on-campus program involved weekly visits to participating teachers to observe them, review and critique materials, and present model demonstrations. The last component, subjective and objective evaluation, consisted of informal classroom observations, a pre- and posttest of science content knowledge, and a Q-sort instrument to assess teacher beliefs about the importance of specific classroom behaviors by teachers. Evaluation results favored the team teaching approach used. (DC)