The prevalence of hyperuricemia was investigated in 214 kidney allograft recipients, 81 were on azathioprine and steroids and 133 on cyclosprine (CyA) and low-dose steroids or on triple therapy. All had stable renal function, serum creatinine < 2.5 mg/dl, and a follow-up between 12 and 120 months. At the time of the study, blood and urine samples were obtained to perform tests of renal function. The renal handling of urate was evaluated by a combined pyrazinamide and probenecid test in 35 selected patients (12 normouricemic on azathioprine, 9 normouricemic on CyA and 14 hyperuricemic on CyA). The prevalence of hyperuricemia was higher in the group of patients on CyA (19.7 vs. 66.9%, p < 0.001), as well as the concentration of serum urate (6.1 ± 1.9vs.7.6 ± 1.7, p < 0.001), and serum creatinine (1.2 ± 0.3 vs. 1.4 ± 0.4, p < 0.001). In patients on CyA, multivariate analysis showed that the most important predictive variables of hyperuricemia were: serum creatinine, FEurate, diuretic use and CyA blood levels (r = 0.73, p < 0.0001). Thirteen patients on CyA (9.9%) had at least one episode of gouty arthritis. Those patients were older than the hyperuricemic patients without gout (45.7 ± 6.7 vs. 37.1 ± 13.5 years, p < 0.01), had worse renal function (serum creatinine 1.9 ± 0.4 vs. 1.5 ± 0.4 mg/dl, p < 0.01), and higher prevalence of hypertension (100 vs. 63.1%, p < 0.05). The combined pyrazinamide-probenecid test showed a lower FEurate during the maximal probenecid-induced uricosuria (p < 0.05) and a lower urate secretion (p < 0.05) in hyperuricemic patients on CyA than in normouricemic on azathioprine or normouricemic on CyA. There were no differences either in the presecretory reabsorption or in the postsecretory reabsorption. According to the previous results, 20 hyperuricemic patients (11 with gouty arthritis) were treated with benziodarone (50-100 mg/day). At 1 month, there was a decrease in the serum urate (10.1 ± 1.8 vs. 5.1 ± 1.4 mg/dl, p < 0.01), and a parallel increase in FEurate (7.1 ± 2.4 vs. 25.4 ± 7.4%, p < 0.001), that persisted after 1 year of follow-up. The drug was well tolerated, and we did not observe side effects. The serum creatinine, CyA dose and CyA blood levels remained unchanged. In conclusion, hyperuricemia is a frequent complication in transplant patients on treatment with CyA. Our data suggest that the disorder could be due to an impairment of the tubular secretion of urate. Benziodarone is an alternative to allopurinol for the treatment of this complication, which does not have important side effects.