Fifty patients had residual urine measured by catheterisation immediately before laparoscopic cholecystectomy. The median amount of urine in the bladder was 100 ml (range 5-500 ml). This urine volume does not distend the bladder enough to risk inadvertant perforation during insertion of a subumbilical port. Urinary bladder catheterisation is unnecessary before laparoscopy especially if the bladder is impalpable.