We report our experience performing simultaneous bilateral percutaneous nephrolithotomy (SBPN) in four patients with large stone burdens in both kidneys. We modified the previously described approach by combining SBPN with subarachnoid Duramorph (preservative-free morphine sulfate) in an effort to decrease postoperative discomfort and shorten the duration of hospitalization. These patients (study group) were then compared with a contemporary group of four patients with similar bilateral stone burdens who underwent staged bilateral percutaneous nephrolithotomies (PCNs) (control group). The comparison showed a marked advantage in hospital stay (4.8 days for the study group v 11 days for the control group) and postoperative narcotic requirement (27.5 mg of meperidine for the study group v 533 mg for the control group). All four patients were rendered stone free. This method of treatment for large bilateral renal calculi with the addition of subarachnoid Duramorph resulted in less postoperative discomfort, less morbidity, and a more rapid recovery than staged PCN or sandwich PCN/SWL/PCN.