Two-hundred patients were hospitalized as an emergency for lower ureteral calculi. Eighty-two of these patients has a less than 6 mm wide calculus which was evacuated by medical treatment; 5 had stagnant infected urine which was drained by endoprosthesis; 113 had an obstructive calculus which resisted medical treatment and was treated by ureteroscopy: the stone could be removed by means of a basket catheter in 58 cases, but this method failed in the other cases and the calculus has to be broken by laser. There were 6 failures due to the nature of the stone (monohydrated oxalate) in 3 cases and to technical laser problems in 3 cases. The success rate of ureteroscopy (basket catheter or laser) was 95 percent in patients whose pain had persisted under medical treatment.