Cephalexin was given to 27 patients with urinary tract infections. Sterilization of the urine after completion of the course of treatment was obtained in 65.5 % of cases. Two months later at least 23 % of the patients treated remained cured. Tolerance of the drug was satisfactory. Important side effects of drug administration were reported in 3 patients (10 %) and minor symptoms, possibly related to the intake of the drug in another two. Although a daily dose of 1 g of cephalexin per day may be sufficient in most cases of urinary tract infections, a regimen of 2 g/ day may offer a desirable margin of safety, without added discomfort. From the experience obtained in the present study, and our previous experience in bronchopul-monary infections, cephalexin appears to be a valuable antibiotic, easy to administer.