During 2002 to 2003, > 2,700 interns nationwide (15% of the students matched via the National Residency Matching Program), mostly from internal medicine programs, completed monthly reports via the Internet that included questions about work, work hours, and sleep. Sleep and work-hour reports were validated by daily diaries, direct observation, and polysomnographic recordings in a randomly selected subgroup, and corroborative information was sought about accidents and injuries. Approximately 17,000 monthly reports were completed. Interns reported an average of 71 h of hospital work per week and four extended shifts per month of a mean duration of 32 h. The survey resulted in three publications30–32 relating work hours to motor vehicle crashes, occupational injuries, and self-reported medical errors. The odds of a motor vehicle crash or a near-miss incident during the home commute after an extended work shift was increased by twofold and fivefold, respectively, compared with those working nonextended shifts.30 Every extended work shift scheduled per month increased the risk of any motor vehicle crash by 9%, and the risk of crash on the home commute specifically increased by 16%. The odds ratio of sustaining a percutaneous injury the day after working overnight was 1.6, compared with an identical time frame on the previous day.31 Lapses in concentration and fatigue were the primary reasons cited by interns for these occupational injuries. Self-reported fatigue-related medical errors were reported during 4% of months with no extended shifts vs 10% of months with one to four extended work shifts and 16% of months with five or more extended work shifts.32 In comparison to months with no extended shifts, the odds ratio for fatigue-related preventable adverse events was 7 for months with five or more extended work shifts. The probability of falling asleep during educational activities and duty, including during surgery, increased in proportion to the number of extended shifts to which one was exposed. The uncertainty of the degree to which acute and chronic partial sleep loss are contributory poses limitations in interpreting these data.