Résumé : Twenty hospitalized adults with lower urinary tract infections received piperacillin sodium intramuscularly 2 grams every 12 hours for 6 to 8 days. Eradication of the causative pathogen was achieved in all patients and was maintained in 14 of them for at least 6 weeks. The mean peak serum level, determined one hour after the 2-gram intramuscular dose, was 40 ug/ml (11-94). Minor side effects were observed including a slight and reversible elevation of blood urea in 3 subjects who had received - concurrently or recently - moderate doses of furosemide.