Enoxacin, a new orally absorbed broad spectrum anti-microbial agent, was used to treat 25 patients with moderate or severe urinary tract infections. Many were complicated and associated with renal insufficiency. Eighteen of the 25 were cured, five had a relapse and two became reinfected with a resistant Streptococcus faecalis. Fourteen of the patients reported side effects, including six with a neurological syndrome, one with widespread arthralgia and one with an Achilles tendonitis. Further studies are indicated with this potent drug to assess its role in the management of severe or complicated urinary infections and to assess the optimum dose and duration of therapy.