When a constructivist professional development program was introduced to elementary teachers in a school district, some of the teachers who teach in self-contained classrooms (N=59) elected to participate in a yearlong professional development project. To explore the impact of professional development, a purposive sample of participating teachers was selected and interviewed in depth one year following the professional development program. The questions focus on the long-range impact of the professional development program on science instruction in classrooms, on the teachers' attitudes toward science teaching and learning, and the barriers that they perceive to science education reform at the building and district levels. Teachers were observed and interviewed on site, student-developed artifacts were examined, and an on site focus group was conducted. Results suggest that when given the freedom to make choices about their own professional development, teachers construct programs which lead to changes in their thinking about teaching and learning. (Author/DDR)