Background: Significant discordance arose between screening mammography clinical practice guidelines published by different national health care organizations following the release of the U.S. Preventive Services Task Force (USPSTF) guidelines in 2009. This allowed for greater interprovider variation in clinical practice while remaining within standard of care. The objective of this study was to determine how differences in patient screening mammography rates between internal medicine physician subgroups defined by gender and level of training changed, if at all, following the release of the new guidelines. Methods: The study was an observational study including all internists and internal medicine residents at a single academic medical center, Dartmouth-Hitchcock Medical Center. Screening mammography rates were determined for patients of subgroups of internists defined by gender and level of training (attending vs resident physician) for the 2 years before and after the release of the updated screening guidelines. Results: Patients having female attending internists as their primary care provider were more likely to undergo screening mammography than those having male attending or resident internists of either gender both before and after the release of the new guidelines, with the difference in patient screening mammography rates between physician subgroups increasing following their release (rates before and after, respectively, by subgroup: female attending = 67%, 64%; male attending = 56%, 50%; female resident = 58%, 41%; male resident = 55%, 41%; P<.05). Conclusions: Internist gender and level of training are associated with differences in patient screening mammography rates at one academic medical center, with these differences increasing following the 2009 USPSTF guidelines. These findings suggest that the correlation between provider gender/level of training and a woman's likelihood of undergoing a screening mammogram strengthened as discordance arose between clinical guidelines published by different medical and health care advocacy groups. It is important for providers and patients both to be aware of correlations that exist between provider characteristics and patient cancer screening rates and to take steps to minimize the impact of provider bias on the shared decision-making process.