Ro 13-9904, a new broad-spectrum, beta-lactamase-resistant, cephalosporin, was given as a single i.m. injection at doses of 500, 250, and 125 mg in 3 groups of male patients each consisting of 10, 6, and 6 patients respectively, suffering from uncomplicated acute but recurrent gonococcal urethritis. All patients were cured both clinically and bacteriologically without relapsing after a 7-day follow-up. 11 patients suffering from chronic urinary tract infections without flow obstruction but with underlying chronic pyelonephritis in 6, were treated for 7 days with 500 mg of Ro 13-9904 i.m., every 12 h. E. coli and P. mirabilis were the main isolated pathogens. Treatment was successful in all with only one bacteriological relapse during the follow-up period. The drug's tolerance was satisfactory except for moderate local pain in most of the patients.