Urinary tract infection (UTI) is a common complication of pregnancy. Approximately 20--40% of women with asymptomatic bacteriuria will develop pyelonephritis during pregnancy. All pregnant women, therefore, should have their urine cultured at their first visit to the clinic. In a clinical study comparing single-dose treatment with 3 g fosfomycin trometamol versus a 3-day course of 400 mg ceftibuten orally, the inclusion criteria were acute symptomatic lower UTI (acute cystitis), significant bacteriuria (> or =10(3) CFU/ml), pyuria and confirmed pregnancy. Excluded were patients with asymptomatic bacteriuria or acute pyelonephritis. Predisposing factors comprised a history of recurrent UTI, diabetes mellitus, analgesic nephropathy, hyperuricaemia or Fanconi's syndrome. Escherichia coli was the most frequently isolated pathogen in both groups. Therapeutic success (clinical cure and bacteriological eradication of uropathogens) was achieved in 95.2% of the patients treated with fosfomycin-trometamol versus 90.0% of those treated with ceftibuten (P, non-significant). The treatment of acute cystitis in pregnant women using a single-dose of fosfomycin trometamol was equally effective as the 3-day course of oral ceftibuten. Both regimens were well tolerated with only minor adverse effects. Long-term chemoprophylaxis should be suggested in patients with recurrent UTI or following acute pyelonephritis during pregnancy.