INTRODUCTION AND AIM: The Australian general practitioner (GP) teaching workforce will need to expand in order to provide for the increasing number of medical students and doctors-in-training. Understanding factors that motivate GPs to become involved in teaching in their clinical practice environments is important for developing recruitment and retention strategies. METHOD: Thirty-one semi-structured interviews were conducted with a cross section of GP teachers and were subjected to thematic analysis. Themes were identified and further classified as motivations and prerequisites for teaching. RESULTS: The desire to update clinical knowledge was the most frequently mentioned motivation for teaching, and was described as a strategy for GP teachers to preserve clinical competence through the opportunity to learn new aspects of medicine from junior colleagues. Other motivations included personal fulfillment and enjoyment of teaching, the opportunity to pass on general practice skills and knowledge, promoting general practice as a career, and fulfilling a sense of responsibility to the profession and community. Peers, students and patients also influenced the decision to teach. Most GPs identified that time, workload, availability of space and adequate financial remuneration were prerequisites for teaching. Practice owners also often determined the GP teachers' capacity to teach. DISCUSSION: To increase the recruitment and retention of GP teachers, it is recommended that teaching organisations give more recognition to teaching as a clinical professional development activity, place more emphasis on GPs' personal enjoyment, professional responsibility and pride in teaching, and increase engagement with practice owners.