The purpose of this ongoing project is to establish a model for school-based teacher development for secondary science and mathematics teachers in Taiwan. The model uses an action research approach with emphasis on constructivist perspectives of teaching and learning and the idea that teachers are to be taken as researchers and reflective practitioners. Implementation strategies for initiating such a collaborative teacher development project that were tested in one of the participating secondary schools are reported. The professional development of the participating teachers was studied by collecting data from sources such as surveys, questionnaires, and interviews. Results from preliminary analysis of the data collected indicate that while some teachers seemed to benefit greatly from this collaborative research, there were a few who were opposed to the project. Influencing factors for the practicability and effectiveness of the school-based professional development project are discussed. (WRM)