The results of 600 consecutive renal transplant operations (540 cadaver and 60 living related donor) in 491 patients were assessed with respect to urological complications. In nearly all cases the ureter was inserted into the bladder using a Leadbetter-Politano ureteroneocystostomy technique. The bladder was drained by Foley catheter for 5 days and the operation site by vacuum drain for a variable period. After 26 operations in 26 patients, 27 episodes of ureteric obstruction were identified (one reobstruction). These occurred between 1 day and 45 months after transplantation and involved the lowest third of the ureter 19 times, the middle third 3 times and the proximal third 4 times. They were due to stricture (11), pelvic collection (7), redundant or twisted ureter (3) or other cause (5). An anatomical predisposing factor in either patient or graft was identified in 31 per cent of these caes. After 18 operations in 18 patients, 21 episodes of urine leakage were identified (three re-leakages). These occurred between 1 day and 6 months after transplantation and an anatomical predisposing factor in either patient or graft was present in 59 per cent. Thus, overall, 7 per cent of patients developed a urological complication in this series. This rate has declined in recent years in parallel with a general reduction in steroid dose for immunosuppression. This last feature, combined with the surgical technique described, has resulted in a low incidence of urological complication after transplantation, being now between 1 and 2 per cent.