Amikacin was used in the treatment of 56 serious gram-negative infections in 54 patients of whom 47 survived. In six of the seven nonsurvivors, the infections were under control at the time of death. The clinical isolates were multiple drug-resistant gram-negative organisms, with Proteus rettgeri being most common. Forty-five (80%) of these infections were nosocomial in origin, and the genitourinary tract was the source in 39 (70%). Complications directly related to amikacin therapy were few and suggested renal or otologic toxicity. In this series of patients, amikacin appeared to be of therapeutic benefit in the treatment of serious gram-negative infections.