An Inquiry Learning Partnership (ILP) for professional development (PD) was formed between a university, science centre, and two urban school districts to offer 4-6th grade teachers specific science content and pedagogical techniques intended to integrate inquiry-based instruction in elementary classrooms. From pre/post content exams, PD surveys, focus group, and assessment data, teachers increased their science content knowledge, reported implementing inquiry practices in their classrooms and their students experienced modest gains on 5th grade standardized science achievement exams. While some teachers were transferring knowledge/skills gained in professional development to their classrooms, others encountered barriers to implementing PD. These obstacles included limited resources, time constraints, mandated curriculum pacing, language learning, and classroom management issues. Strategies to mitigate these barriers in order to maximize the impact of professional development need to be a priority in professional development reform. (Contains 2 tables and 3 figures.)