In recent years professional developers have reached a consensus about what constitutes effective professionaldevelopment, referred to in the literature as “learner-centered professional development.” InterMath is a professional development project that was developed to address the recommendations for high quality professional development for middle grades mathematics teachers. In this report, I will highlight two cases of InterMath implementation. Then, I will offer a discussion of changes that have been made to InterMath in light of the findings from the pilot studies and report preliminary analysis of the impact of these changes.