In order to evaluate the efficacy and safety of fosfomycin trometamol as single dose oral treatment for acute cystitis in women, an open, multicenter comparative study was carried out in general practices in France, 386 women, aged 16 to 75 years, with clinical symptoms of acute cystitis were enrolled in the study to receive either a single 3 g oral dose of fosfomycin trometamol or a five-day course of 400 mg pipemidic acid twice daily. The diagnosis of cystitis was based on clinical symptoms and significant bacteriuria (greater than or equal to 10(5) cfu/ml midstream urine). Follow-up examinations were carried out five to ten and 28 days after the end of treatment, 289 and 244 patients, respectively, were available for clinical and bacteriological evaluation at short-term (five to ten days) and medium-term (28 days) post-treatment follow-up. Both regimens were comparable for clinical and bacteriological efficacy with short-term eradication rates of 122/146 in the fosfomycin trometamol group and 130/143 in the pipemidic acid group. The results of medium-term follow-up were 113/122 and 114/122 for the eradication rates of the respective groups. Both drugs were well tolerated. Side effects were mild and of significantly shorter duration in the fosfomycin trometamol group.