Context: Morbidity and mortality conferences in residency programs are intended to discuss adverse events and errors with a goal to improve patient care. Little is known about whether residency training programs are accomplishing this goal. Objective: To determine the frequency at which morbidity and mortality conference case presentations include adverse events and errors and whether the errors are discussed and attributed to a particular cause. Design, Setting, and Participants: Prospective survey conducted by trained physician observers from July 2000 through April 2001 on 332 morbidity and mortality conference case presentations and discussions in internal medicine (n = 100) and surgery (n = 232) at 4 US academic hospitals. Main Outcome Measures Frequencies of presentation of adverse events and errors, discussion of errors, and attribution of errors. Results: In internal medicine morbidity and mortality conferences, case presentations and discussions were 3 times longer than in surgery conferences (34.1 minutes vs 11.7 minutes; P = .001), more time was spent listening to invited speakers (43.1% vs 0%; P<.001), and less time was spent in audience discussion (15.2% vs 36.6%; P<.001). Fewer internal medicine case presentations included adverse events (37 [37%] vs 166 surgery case presentations [72%]; P<.001) or errors causing an adverse event (18 [18%] vs 98 [42%], respectively; P = .001). When an error caused an adverse event, the error was discussed as an error less often in internal medicine (10 errors [48%] vs 85 errors in surgery [77%]; P = .02). Errors were attributed to a particular cause less often in medicine than in surgery conferences (8 [38%] of 21 medicine errors vs 88 [79%] of 112 surgery errors; P<.001). In discussions of cases with errors, conference leaders in both internal medicine and surgery infrequently used explicit language to signal that an error was being discussed and infrequently acknowledged having made an error. Conclusions: Our findings call into question whether adverse events and errors are routinely discussed in internal medicine training programs. Although adverse events and errors were discussed frequently in surgery cases, teachers in both surgery and internal medicine missed opportunities to model recognition of error and to use explicit language in error discussion by acknowledging their personal experiences with error.