Adverse events in hospitalized patients often go unrecognized or unreported. The authors developed a confidential reporting method for identifying adverse events in a medicine unit of a teaching hospital. House officers were interviewed during morning rounds and by email, and the interviews were compared with hospital incident reports and patients’ medical records. The study found that adverse events occurred in 2.6% of all admissions. The most common problems were related to inadequate evaluation of the patient, failure to monitor or follow-up, and failure of the laboratory to perform a test. The hospital incident reporting system only identified 1 out of 57 house officer-reported adverse events. The authors propose using confidential peer interviews of front-line providers to improve identification of medical errors and to improve overall quality of care.