The outcome of suprapubic and urethral catheterization in abdominal surgery was compared in a prospective randomized trial. Twenty-eight patients received a suprapubic and 29 a urethral catheter. The groups were similar in terms of age, sex, operation performed and postoperative analgesia. There was no difference in the duration of catheterization (suprapubic: median 5 (range 4-10) days; urethral: median 4 (range 2-11) days). Urinary sepsis occurred in three patients in each group. Urethral catheters caused pain in significantly more patients (urethral 13; suprapubic two; chi 2 = 8.6, 1 d.f. P < 0.01), on more days (suprapubic: 6 of 142 catheter days; urethral: 37 of 126 catheter days; chi 2 = 29.5, 1 d.f. P < 0.001). Two men with urethral catheters and one with a suprapubic catheter failed to void urethrally when required to do so. Suprapubic catheterization is the method of choice for urinary drainage when this is required in abdominal surgery.