This study uses a sample of 454 teachers engaged in an inquiry science program to examine the effects of different characteristics of professional development on teachers' knowledge and their ability to implement the program. The authors analyzed results from a survey of teachers served by 28 professional development providers within a hierarchical linear modeling framework. Consistent with findings from earlier studies of effective professional development, this study points to the significance of teachers' perceptions about how coherent their professional development experiences were for teacher learning and program implementation. The authors also found that the incorporation of time for teachers to plan for implementation and provision of technical support were significant for promoting program implementation in the program. (Contains 4 tables.)