PURPOSE: Complex surgical procedures are migrating out of hospitals and into ambulatory surgery centers. We evaluated the extent to which surgery for urolithiasis could be a candidate for such migration. MATERIALS AND METHODS: Patients undergoing stone surgery in Florida (107,417) between 1998 and 2004 were included in the study. Poisson models were fit to assess temporal changes in the setting (inpatient, outpatient and ambulatory surgery center) and type (open, percutaneous, extracorporeal, ureteroscopy and stenting) of stone surgery. For inpatient procedures secular trends in comorbidity burden (0 or 1 diagnoses vs 2 or more) and procedure acuity (elective vs emergency) were also assessed. Admission requirements and mortality rates were measured according to the surgery setting. RESULTS: Of the 107,417 discharges from 1998 to 2004 surgery rates per 100,000 increased from 35.5 to 38.2 for inpatients (p <0.05), 84.2 to 104.7 for hospital outpatients (p <0.01) and 9.4 to 26.9 for ambulatory surgery centers (p <0.01). For hospitalized patients routine admissions decreased (41.8% to 29.5%, p <0.01) and procedure acuity increased (16.8% to 28.2%, p <0.01). No deaths occurred at ambulatory surgery centers and the rate of admission to acute care hospitals was 2.5/100,000 cases. CONCLUSIONS: Despite the safety and efficiency of ambulatory surgery centers hospital outpatient departments remain the preferred setting for urinary stone surgery. For patients requiring surgical intervention for urinary stone disease ambulatory surgery centers could be an underused resource.