'Background': Is teaching a medical student always a financial burden on rural general practice? If so, is the current trend towards increasing placement of students in rural practice sustainable? Retrospective studies of short-term attachments to rural general practice have repeatedly shown a financial cost to the practice. Might the results be different for extended attachments? This paper presents the results of a small prospective study of the financial impact of undergraduate medical students undertaking the Parallel Rural Community Curriculum, a 12 month clinical attachment to rural general practice in the Riverland region of South Australia. 'Methods': Students and doctors involved in the program kept separate logs of patient contact time. These data were triangulated with third-party direct observation of consultations and an exit questionnaire on patient satisfaction. 'Results': In this study, where students had already been actively involved in all aspects of the practice for at least 5 months, it was found that students had a positive effect on general practitioner productivity, without any loss in patient satisfaction. 'Discussion': To account for these findings, a hypothetical model has been developed of the financial impact of a student on a rural general practice over time. With the current trend in medical schools to undertake increasing amounts of teaching in rural general practice, it is suggested that it may be more economically sustainable if curricula are adapted to allow extended attachments, likely to be at least 5-6 months, rather than traditional shorter rotations.