BACKGROUND Low salaries and difficult work conditions are perceived as a major barrier to the recruitment of primary care physicians to rural settings. OBJECTIVE To examine rural-urban differences in physician work effort, physician characteristics, and practice characteristics, and to determine whether, after adjusting for any observed differences, rural primary care physicians' incomes were lower than those of urban primary care physicians. METHODS Using survey data from actively practicing office-based general practitioners (1,157), family physicians (1,378), general internists (2,811), or pediatricians (1,752) who responded to the American Medical Association's annual survey of physicians between 1992 and 2002, we used linear regression modeling to determine the association between practicing in a rural (nonmetropolitan) or urban (standard metropolitan statistical area) setting and physicians' annual incomes after controlling for specialty, work effort, provider characteristics, and practice characteristics. RESULTS Rural primary care physicians' unadjusted annual incomes were similar to their urban counterparts, but they tended to work longer hours, complete more patient visits, and have a much greater proportion of Medicaid patients. After adjusting for work effort, physician characteristics, and practice characteristics, primary care physicians who practiced in rural settings made $9,585 (5%) less than their urban counterparts (95% confidence intervals: -$14,569, -$4,602, P < .001). In particular, rural practicing general internists and pediatricians experienced lower incomes than did their urban counterparts. CONCLUSIONS Addressing rural physicians' lower incomes, longer work hours, and greater dependence on Medicaid reimbursement may improve the ability to ensure that an adequate supply of primary care physicians practice in rural settings.