We have performed, between May 1985 and December 1988, in situ lithotripsy in 100 consecutive cases of primary ureteral stones, using electrohydraulic lithotripsy in 33 patients and ultrasonic lithotripsy in the remaining 67. After using similar instruments and surgical techniques in both groups, we have comparatively evaluated the complications encountered and the results obtained. With the electrohydraulic lithotripsy we have obtained a complication rate of 42% (operative and postoperative) and favorable results in 72.7% of the patients; using ultrasonic lithotripsy, the complication rate was 10.4%, and favorable results were obtained in 92.5%. We conclude that, at least in our experience, ultrasonic lithotripsy is less invasive and more successful than electrohydraulic lithotripsy in the treatment of primary stone disease.