The objective of the study was to assess the effects of low-dose vaginal treatment with oestradiol before vaginal operation. In a double-blind randomized study including 43 postmenopausal women scheduled for vaginal repair operation for genital descensus, it was found that 7 patients suffered from concomitant urinary stress incontinence. Vagifem (25 micrograms oestradiol) or placebo was administered as vaginal pessaries daily, 3 weeks prior to surgery and the clinical effects evaluated. One month postoperatively the prevalence of bacteriuria (> 100,000 CFU/ml urine) was significantly lower when using oestradiol than in the placebo group. At follow-up 3 years later 40 women (93%) answered the questionnaires. None received hormone replacement therapy. Nineteen percent in the preoperative oestradiol group and 11% in the preoperative placebo group had had more than two episodes of cystitis treated with antibiotics. This difference is not statistically significant (p > 0.05). Recurrent cystitis was not correlated to bacteriuria postoperatively. Seventy-nine percent of the women with genital prolapse but only 29% of the women with concomitant urinary stress incontinence were cured (p < 0.05). Neither preoperative oestradiol treatment nor body weight had any influence on relapse. Preoperative low-dose vaginal oestradiol treatment may reduce the incidence of bacteriuria in the immediate postoperative period but no long-lasting effects on recurrent cystitis or relapse were seen. Longer-lasting hormone replacement therapy may be necessary to achieve lasting effects.