OBJECTIVE To assess the efficacy of oral oestriol in the prevention of recurrent urinary tract infections in elderly women. METHODS Double-blind, randomised, parallel group, placebo controlled trial METHODS Urogynaecology Unit at King's College Hospital with some women recruited from the geriatric units of St. Pancras Hospital and Dulwich Hospital, London (UK). METHODS Seventy-two postmenopausal women older than 60 years of age (mean 73.2 years) suffering from recurrent urinary tract infections. METHODS Oral oestriol (3 mg per day) or placebo for six months. MAIN: outcome measures Urinary tract infection rates. RESULTS The study was difficult to conduct because of its design and the age of the participants. Oral oestriol (3 mg per day) was not shown to be superior to placebo in the prevention of recurrent urinary tract infections, but both oestriol and placebo improved urinary symptoms during the trial. CONCLUSIONS The power of the study might have been too low to detect a significant difference between the groups, or oral oestriol (3 mg per day) may have been either the wrong dose or the wrong route of administration for this indication.