A total of 1016 consecutive renal transplants performed between 1976 and 1990 were analysed retrospectively to determine the incidence of urological complications and possible predisposing factors. Some 189 episodes of ureteric obstruction and/or urinary leak occurred in 143 patients (overall incidence 14.1%). The median annual rate of urinary leak was 5.1%; that of ureteric obstruction was 4.5% pre-1986 and 16.1% post-1986. Sixty-three episodes of urinary leak occurred in 54 patients from 1 day to 3 months post-transplant and 60% involved the distal ureter. Thirty were treated primarily by reconstructive surgery, ten required nephrectomy and three died of associated sepsis. A total of 126 episodes of ureteric obstruction occurred in 104 patients from 1 day to 12 years post-transplant and 86% involved the distal ureter. Prior to 1986, 10/11 patients with ureteric obstruction were treated by reconstructive surgery, but since then 88 (95%) have been treated by percutaneous nephrostomy, with or without stenting, with only one graft lost and no deaths. Children had a significantly increased incidence of ureteric obstruction (P < 0.001) whilst male recipients had an increased incidence of urinary leak (P = 0.04). More patients with ureteric obstruction than those without had two or more episodes of rejection (P = 0.03). No single cause for the increased incidence of ureteric obstruction since 1986 has been identified. Continued attention to technical detail and further study of this trend is warranted.