Indwelling urethral catheters are the most common cause of urinary tract infections (UTI), yet there is no direct evidence that technique of catheter insertion affects this. In a prospective study, 156 patients underwent preoperative urethral catheterisation, randomly allocated to 'sterile' or 'clean/non-sterile' technique groups. There was no statistical difference between the two groups with respect to the incidence of UTI. There was a considerable cost difference between the two groups, the 'sterile' method being over twice as expensive as the 'clean' method. Strict sterility is not necessary in preoperative short-term urethral catheterisation and is more expensive and time consuming.