Objectives. To determine when emergent intervention for bleeding after percutaneous nephrolithotomy (PCNL) is required. Methods. We reviewed analysis data of 850 patients who had undergone PCNL in our center. Blood transfusion was needed for 60 (7%) patients during and/or after surgery. We routinely performed followup of the urine output per hour, blood pressure, and hemoglobin levels after PCNL. Five (0.6%) of them had severe bleeding that emergent intervention was needed. Results. The mean age of the 5 patients who had emergent surgery due to severe bleeding was 42.2 (19-56) years. Mean duration of surgery was 44.75 (25-65) minutes. Mean stone size was 27 (15-38) mm. Mean decrease of hemoglobin was 4.8 (3.4-5.8) ng/dL, and unit of transfused blood was 4.4 (3-6). Mean blood pH was 7.21. There were metabolic acidosis and anuria/oliguria in all these patients. One of 5 patients suffered from cardiopulmonary arrest because of massive bleeding four hours after the PCNL, and despite cardiac resuscitation, he died. Hemorrhaging was controlled by open surgery in the other 4 patients. Two patients experienced cardiac arrest during the open surgery but they responded to cardiac resuscitation. There were no metabolic asidosis and anuria/oliguria, and bleeding was managed only with blood transfusion for the other 55 patients. Conclusion. Severe bleeding after PCNL is rare and can be mortal. If metabolic asidosis and anuria/oliguria accompanied the drop of hemoglobin, emergent surgical intervention should be performed because vascular collapse may follow, and it may be too difficult to stabilise the patient.