During the 9-year period from 1972 to 1980, 1069 cases of urolithiasis were seen in the Department of Urology, Okayama University Hospital. The ratio of males to females was 2.1 to 1. The maximum incidence of urolithiasis occurred from the third to fifth decade. The overall recurrence rate was 26.7% , and most recurrence (62.1%) occurred 1-3 years following the removal of initial calculi. Concerning renal calculi, the incidence of residual calculi and postoperative recurrence was dependent on the shape and number of calculi rather than operative methods. Mixed calcium oxalate and phosphate calculi were found most frequently, and calculi containing struvite also were found frequently in females. The components of recurrent calculi were identical to those of initial calculi in most cases (72.8%).