The Italian multihospital study of bacteriuria in pregnancy randomized 153 pregnant bacteriuric patients to receive fosfomycin trometamol (FT) as a single dose of 3 g and 138 such patients to receive conventional therapy with pipemidic acid (PA), 400 mg b.i.d. for 7 days. The two groups were well matched for age, parity, pregnancy course, symptoms and past history of cystitis. Infecting organisms were eradicated in 147 (96%) of FT and 129 (94%) of PA patients. Similar recurrence rates occurred. Minimal side effects (mostly nausea and dyspepsia) occurred (9% FT; 15% PA). Single-dose FT appeared equivalent to conventional treatment with PA.