This research focused on physical education (PE) teaching and learning in New Zealand primary school settings. The project had two key aims: first, to develop an understanding of the knowledges primary teachers use to teach PE, prior to a one-year professional development (PD) programme; and second, to evaluate the impacts of a PD programme on knowledges associated with teaching PE, and the complexity of subject specific knowledge development for generalist teachers. Specifically, the impact of the Physical Activity Initiative professional development (PD) programme (Ministry of Education, 2005a) on primary classroom teacher's knowledge and practice was investigated. The project was interpretive in orientation and used qualitative methods such as teacher interviews, lesson observations, questionnaires and document analysis to gather data related to teachers' understanding of their pre and post PD programme experience. Twenty-five teachers from ten schools involved in the Physical Activity Initiative PD programme participated in the study. Theories of teacher knowledge and understandings of effective PD provided a framework for data analysis. In contrast to most previous studies that have involved the researcher as both instigator and deliverer of physical education professional development (PE-PD), this research involved the researcher as the outsider, seeking an outside-in and inside-out perspective. The research findings indicated that promoting teacher learning through PD is complex. The sample of primary school teachers gained benefit from PD opportunities that allowed for the transfer of pedagogical strategies and skills from the classroom to the PE context. However, there was evidence that these learning opportunities needed to be balanced with opportunities to develop PE content knowledge. Consequently, it was theorised that PE-PD for primary teachers needs to consist of connected and explicit knowledge building experiences associated with PE: its nature, purpose, curriculum, content, and pedagogical strategies. It was further hypothesised that effective PE-PD design would support teachers to blend these knowledges in ways that allow them to develop appropriate learning experiences for their particular students. The findings also signalled that PD resources provided teachers with examples of practice and, as such, they had the potential to enhance quality PE learning and teaching. The study drew attention to the role resources played in standardising PE in primary schools, thus advancing PE teaching yet restricting teachers' broader knowledges and limiting their range of practices in PE. The findings of this study challenge PD providers (pre- and in-service) to consider the educative role of resources and the ways resources can be used to support teachers to become independent practitioners who utilise outside 'experts' without becoming totally reliant on them. Finally this study illustrates the importance of recognising the teacher as both learner and teacher. It is imperative that teacher learning sits alongside student learning as a central aim for PD programmes, since teacher learning is the foundation for changes in learning outcomes for students.