This paper provides a detailed description and evaluation of a three-year professional development project in a large urban setting in the southwestern United States. The impetus for the project was curriculum development focused on integrated scientific inquiry. Project goals included the development of a professional learning community, reformed teacher practice, and improved content knowledge for teachers and their students. Annually, a two-week summer institute was provided for approximately 50 high school science teachers with graduate-level coursework during the academic year. The results document improvements in teacher content knowledge and key changes in the classroom characteristics of teacher participants. Further, students enrolled in a target course with teachers who participated fully in the professional development were more than twice as likely to pass the state science examination. The results from this project add to what is known about delivering successful, contextually relevant professional development. (Contains 5 tables and 3 figures.)