In general practice acute uncomplicated urinary tract infections in women are treated with different courses of antibiotics. In this study the efficacy and tolerability of a single dose of 3 g fosfomycin trometamol and the conventional treatment with nitrofurantoin 50 mg four times daily for seven days were compared. In a randomized, double-blind, double-dummy trial in 31 general practices in the Netherlands 231 patients with symptoms of acute dysuria, stranguria and/or urinary frequency received treatment. Evaluation was based on resolution of symptoms, dipslide results and side-effects at 4, 9 and 42 days after starting the treatment. The clinical cure rates and bacteriological cure rates were not significantly different between the treatment groups. Side-effects were reported at day 4 by 43% of the women receiving single-dose treatment, compared with 25% of the women in the seven-day treatment group, a significant difference. At day 9 the groups did not significantly differ in the number of patients with side-effects. Almost all side-effects were mild and gastro-intestinal complaints were reported most. Taking into account the convenience of taking a single dose we conclude that fosfomycin trometamol is a reasonable alternative to 7 days nitrofurantoin 50 mg four times a day in the treatment of women with symptoms of acute uncomplicated urinary tract infections in general practice.