['To determine whether physician specialty is associated with prescription of warfarin to elderly persons with atrial fibrillation.', 'Cross-sectional survey.', 'One hundred and thirty-eight randomly selected general practitioners--all 58 internists and all 27 cardiologists in southern Alberta were surveyed by mail.', 'Physicians identified their preferred drug for stroke prevention generally and in response to two hypothetical cases.', 'Response rates were 66% (general practitioners), 76% (internists) and 89% (cardiologists). Specialists (92%) were more likely than general practitioners (76%) to choose warfarin (P = 0.007). Findings were similar for questions related to case scenarios; however, the magnitude of differences between specialists and general practitioners was less pronounced. Specialists were more likely (77%) to prescribe warfarin for elderly females than were general practitioners (62%, P = 0.08). Similar proportions of specialists (77%) and general practitioners (67%) would prescribe warfarin to elderly males.'] Is physician specialty associated with differences in warfarin use for atrial fibrillation?