This study analyzed nearly 5 million admissions to determine if patient safety is truly compromised on weekends. Complication rates were determined for specific surgical and obstetric procedures by using the Agency for Healthcare Research and Quality's (AHRQ) Patient Safety Indicators, with extensive adjustment for comorbid conditions and other confounders. Overall complication rates were modestly but significantly increased for some obstetric indicators and for vascular surgical procedures. The study adds to prior research documenting that patients with an acute myocardial infarction, or other conditions requiring urgent treatment, have increased mortality if admitted on a weekend.