Urinary citrate is an important determinant for crystallization of calcium salts, and recently oral administration of citrate has been suggested to be clinically useful in the management of renal stone disease. The effect of CG-120, a citrate compound (potassium citrate, sodium citrate and citric acid) produced by Dr. Madaus (Germany), on upper urinary tract stones was investigated in 398 patients in this study group. The patients were treated with 3 or 4 g CG-120 daily. Two hundred thirty-one of them were treated accurately according to the protocol of the study for more than 32 weeks. The cumulative percentage of positive clinical effect for the stone (disappearance, passage or decrease in size) was 30.3% (70/231). There were no differences in the clinical effect between the group of 3 g/day and the group of 4 g/day. CG-120 seemed to be more effective in the cases of ureteral stone, young patients and females, but was less effective in the recurrent stone formers. Although there were 45 episodes of side effects in 38 patients in this study, no serious side effects attributed to CG-120 were experienced. CG-120 was proved as a useful drug in the treatment of upper urinary tract calculi as well as its prevention.