40 patients were given a single, short intravenous infusion of 4 g fosfomycin over a period of five to ten minutes. In 23 patients, the contents of the gall bladder were removed intra-operatively 30-105 minutes after the fosfomycin infusion. In 17 patients who had undergone cholecystectomy eight to ten days earlier, bile was obtained via a T-drain 30, 60, 120, 240 and 360 minutes after the fosfomycin infusion. Fosfomycin concentrations of 1-196 mg/l were present in the bile which had been removed intra-operatively. No correlation was found between the concentration and the time of removal. Patients with the highest alkaline phosphatase in serum, however, had the lowest fosfomycin concentrations. In the patients with T-drains, the highest concentrations (93 mg/l) were found 30 minutes after the fosfomycin infusion. By the sixth hour the concentrations had fallen to 19 mg/l.