There is considerable interest in preparing science teachers who can implement reform-based practices in schools. However, there are relatively few research programs that have systematically studied the implementation of this teaching innovation over extended time (i.e., the entire undergraduate experience and the first few years of full time teaching practice). One extended research program since 1993 that has examined this critical issue in teacher preparation has been carried out in a National Science Foundation funded project in the Collaboratives for the Excellence in Teacher Preparation Program (CETP), the Maryland Collaborative for Teacher Preparation (MCTP). This session synthesizes and reflects on the key research insights coming from over twenty separate studies conducted within the MCTP Research Program over nine years. A significant finding is that the MCTP new teachers maintain their reform-based orientation over time even as they report that they find many school environments resistant to reform-based practices. (Author)