BACKGROUND: There is growing concern that the quality of inpatient care may differ on weekends versus weekdays. We assessed the "weekend effect" in common urgent general operative procedures. METHODS: The Healthcare Cost and Utilization Project Florida State Inpatient Database (2007-2010) was queried to identify inpatient stays with urgent or emergent admissions and surgery on the same day. Included were patients undergoing appendectomy, cholecystectomy for acute cholecystitis, and hernia repair for obstructed/gangrenous hernia. Outcomes included duration of stay, inpatient mortality, hospital-adjusted charges, and postoperative complications. Controlling for hospital and patient characteristics and type of surgery, we used multilevel mixed-effects regression modeling to examine associations between patient outcomes and admissions day (weekend vs weekday). RESULTS: A total of 80,861 same-day surgeries were identified, of which 19,078 (23.6%) occurred during the weekend. Patients operated on during the weekend had greater charges by $185 (P < .05), rates of wound complications (odds ratio [OR] 1.29, 95% confidence interval [95% CI] 1.05-1.58; P < .05), and urinary tract infection (OR 1.39, 95% CI 1.05-1.85; P < .05). Patients undergoing appendectomy had greater rates of transfusion (OR 1.43, 95% CI 1.09-1.87; P = .01), wound complications (OR 1.32, 95% CI 1.04-1.68; P < .05), urinary tract infection (OR 1.76, 95% CI 1.17-2.67; P < .01), and pneumonia (OR 1.41, 95% CI 1.05-1.88; P < .05). Patients undergoing cholecystectomy had a greater duration of stay (P = .001) and greater charges (P = .003). CONCLUSION: Patients undergoing weekend surgery for common, urgent general operations are at risk for increased postoperative complications, duration of stay, and hospital charges. Because the cause of the "weekend effect" is still unknown, future studies should focus on elucidating the characteristics that may overcome this disparity.