Objective: This study describes medical students' perceptions about resident teaching on a surgery clerkship and examines student perceptions before and after the implementation of duty hours regulations (DHR)., Summary Background Data: There has been much discussion about the impact of DHR on surgical education. One area that merits evaluation is the effect that DHR have had on student education. Learners perceive the clinical teacher role as comprised of 4 roles: teacher, person, physician, and supervisor. This model served as the basis for examining resident teaching before and after DHR., Methods: Students completed end-of-rotation evaluations about residents' teaching effectiveness, amount of feedback, and quality of interactions. Student comments were compiled into individual resident reports, and reports were collected from pre- (2002-2003) and post- (2003-2004) DHR. A coding scheme was developed to describe resident performance in 4 roles: teacher, person, physician, and supervisor. Three coders independently reviewed 124 resident reports maintaining an interrater agreement of 80%. Analyses of variance were conducted to compare data from pre- and post-DHR., Results: After implementation of DHR, there were significantly more negative comments (P = 0.005), including comments about residents as supervisor (P = 0.001), teacher (P = 0.027), and teaching activities (P = 0.001). Positive comments about bedside teaching decreased (P = 0.007). Although total positive comments about resident as person increased (P = 0.01), total negative comments about resident as person also increased (P = 0.02)., Conclusions: Findings of this study indicate that DHR have had a negative impact on medical students' perceptions of resident teaching. Surgical educators must develop programs that address resident teaching skills in a different environment.