100 reno-ureteric calculi have been treated by the same operator between April 1984 and November 1986 by means of PCNL. 78 of them were greater than 1 cm in diameter, 15 were ureteric and 13 were staghorn calculi. 31 patients had already undergone at least one lumbotomy on the same side. The operation was always performed under general anaesthesia and fluoroscopic control and in 2 stages for the first 20 patients. The mean duration of irradiation was 13 minutes. Total success was obtained in 71 cases (including 10 of the 13 staghorn calculi). 18 cases presented with residual stone debris, equal to or less than 3 mm in diameter in 8 cases. Complete failure was observed in 11 cases and the stone had to be removed surgically (4 cases) or by repeat PCNL (2 cases) or by ECL (5 cases). 9 complications were inconsequential in 8 cases and never required a surgical operation, but 1 severe infection was almost fatal. There were no cases of nephrectomy or loss of renal function. The mean duration of hospital stay was 7 days. 31 patients were lost to follow-up, including 26 without stones. The other 69 patients have been followed for 3 months to 2 years. 5 of the 45 patients discharged from hospital without stones returned with a recurrence. Of the 24 patients with a residual stone fragment (less than 3 mm in diameter in 8 cases), only 2 have eliminated it spontaneously and in 2 other patients the residual fragment has increased in size.(ABSTRACT TRUNCATED AT 250 WORDS)