The institution of work hour regulations for housestaff in 2003 was intended to benefit physicians and patients, as prior research suggested a relationship between physician fatigue and medical errors. In this study, 2700 interns completed monthly surveys asking them to report their work hours and whether patients under their care experienced significant preventable medical errors. Previous articles analyzing the same survey data demonstrated that extended work shifts (working more than 24 consecutive hours) remain common for interns, and working extended shifts is associated with an increased risk of percutaneous injuries (eg, needle sticks). This study found that interns who worked extended shifts were much more likely to report both significant preventable errors and attentional failures (eg, falling asleep at work). An accompanying editorial notes that the laudable impetus to reduce housestaff work hours may result in a "dangerous tradeoff" between reducing work shifts and increasing discontinuity.