['Surgical operations at academic medical centers typically involve a resident physician performing cases together with, and/or under the supervision of, an attending physician. Although this is a widely accepted practice, recent emphasis on patient safety has led to scrutiny about this educational model. There are few studies evaluating whether complication rates, independent of patient risk factors, are affected by resident participation in operations.', 'We identified 295 patients (590 breasts) who had undergone bilateral reduction mammoplasty led by a single attending surgeon between October 1, 1997 and September 30, 2008 at the University of Michigan Health System. In all cases, the attending operated on the right breast and the resident operated on the left breast under the supervision of the attending, allowing each patient to act as their own control. Their charts were retrospectively reviewed and major complications were defined as those requiring either an operation or hospitalization to treat.', 'Twenty-three patients (7.8%) had a major complication after their breast reduction. Ten of these complications occurred in the left breast, 9 in the right breast, and 4 in both breasts. Statistical analysis revealed no differences in major complication rates between the side operated on with the primary surgeon being the resident versus the attending (4.7% versus 4.4%; p = 1.00).'] Does resident participation affect surgical outcomes , despite introduction of new techniques?