In a double-blind placebo controlled clinical trial the preventive value of the antibacterial ointment povidone-iodine 10% (Isodine, Betadine) applied to urethral meatus was evaluated in 17 females suffering from recurrent urinary tract infections (UTI). The patients applied povidone-iodine respectively placebo ointment twice daily and before sexual intercourse in two 6-month periods in a cross-over design. No difference was observed in number of UTI during povidone-iodine and placebo prophylaxis. A decrease in the incidence of UTI was seen during application of any ointment. The antibacterial properties of povidone-iodine ointment is unimportant in the prophylaxis of reinfections as also indicated from urethral and periurethral cultures during the study revealing no change in pathogenic bacterial flora. An improved perineal hygiene in the context of application of ointment may be responsible for the reduction in UTI incidence in females with recurrent cystitis.