Hyperuricaemia is a frequent side-effect of cyclosporin A (CyA) therapy in renal transplant patients, and gout arthritis is the cause of considerable morbidity among these patients. However, neither the potential predisposing factors nor the mechanisms of hyperuricaemia have been clearly elucidated. It has been reported that hyperuricaemia in patients on CyA is associated with a lowered glomerular filtration rate, or with a reduced urate clearance, due to an increase in the net tubular urate reabsorption or to a decrease in secretion. These conclusions are mostly supported by measurements of the basal clearance rate and fractional excretion of urate, but more precise studies of renal handling of urate by the renal tubule have seldom been performed. The purpose of our study was to investigate the prevalence of hyperuricaemia in our population of renal transplant patients, as well as the risk factors involved. Furthermore, we have evaluated the mechanism of hyperuricaemia by a combined pyrazinamide and probenecid test allowing a better evaluation of urate transport processes than pyrazinamide alone.