A prospective randomized controlled double-blind study was performed on 61 patients undergoing transurethral resection of the prostate. The first group of 31 patients received 3 g fosfomycin trometamol p.o. each on the evening before and after the operation; the second group of 30 patients received a placebo. Urine samples were taken by catheter puncture 24 and 48 h postoperative. After removal of the catheter (day 5) the first midstream urine was collected for culture, and from that moment on all patients were treated with a nitrofurantoin derivative for two weeks. Although the same strict antiseptic measures were standard practice for both groups, the incidence of early postoperative urinary tract infections was significantly lower for the fosfomycin trometamol group (0/31 versus 6/30 in placebo recipients). None of the patients suffered from a major symptomatic or complicated infection. There were no side effects registered.