We investigated the clinical efficacy of moxalactam for treatment of a variety of infectious disorders in 50 patients (38 males and 12 females). Patient ages ranged from 8 days to 98 years, with a median of 66 years. Infectious disorders were confirmed by isolation of etiological bacteria in all patients. Thirty-eight patients had gram-negative bacillary disease, nine had pneumococcal infection, and three had disorders caused by staphylococci or streptococci. Twenty-three patients had pneumonia, 17 had bacteremic diseases other than pneumonia, and 10 had miscellaneous infectious diseases. The overall efficacy of moxalactam was excellent. Forty-eight patients were cured by clinical criteria, and 45 were cured by bacteriological criteria. A total of 19 adverse reactions were associated with the use of moxalactam in 18 patients, but none were severe and only one necessitated discontinuation of treatment. Moxalactam promises to be an important addition to our therapeutic armamentarium, especially for therapy of gram-negative bacillary infections.