Hyperuricemia is common in cyclosporine-treated renal allograft recipients. An increased incidence of gout in patients receiving both diuretics and cyclosporine has been reported, but the effect of hyperuricemia on renal allograft function has not been studied. In a prospective, randomized trial of cyclosporine and prednisone versus azathioprine, prednisone, and antilymphocyte globulin for immunosuppression in renal allograft recipients, 105 of 131 cyclosporine and prednisone-treated patients (80 percent) experienced hyperuricemia (serum uric acid level above 8 mg/dl) and 13 of 131 (10 percent) were severely hyperuricemic (serum uric acid level above 14 mg/dl). In contrast, hyperuricemia developed in 63 of 115 patients (55 percent) treated with azathioprine, prednisone, and antilymphocyte globulin (p less than 0.002). Despite the frequent occurrence of hyperuricemia, gout was rare. Clinical gout developed in six patients in the cyclosporine and prednisone group and in 0 patients in the azathioprine, prednisone, and antilymphocyte globulin group between 1 and 43 months (median 22.5 months) after transplantation. Neither severe hyperuricemia nor diuretic therapy were associated with a significantly increased incidence of gout. The mean serum creatinine concentration of severely hyperuricemic patients (all on cyclosporine and prednisone) was similar to that of normouricemic cyclosporine and prednisone patients (1.8 mg/dl versus 1.6 mg/dl, p greater than 0.2), and the severely hyperuricemic patients had a 4-year graft survival rate of 90 percent. Asymptomatic hyperuricemia after renal transplantation does not adversely affect allograft function, requires no specific therapy, and is not a contraindication to use of diuretics.