Amikacin was administered to 18 patients with gram-negative septicemia. Ten of the patients had blood culture isolates highly resistant to gentamicin; six of these patients had persistent bacteremia while receiving gentamicin alone or in combination with other agents. Fourteen of the 18 patients were cured with amikacin therapy and adjunctive measures. Nine of the 10 patients with gentamicin-resistant pathogens were cured. The occurrence of nephrotoxicity in four patients with elevated amikacin serum levels and serious underlying disease indicates the desirability of monitoring serum amikacin levels. Minor ototoxicity occurred in two patients and was associated with prolonged therapy and high serum amikacin levels. Amikacin is a highly effective agent for treating patients with gram-negative bacteremia; it is the agent of choice in the therapy of patients with suspected or documented gram-negative bacteremia caused by pathogens resistant to gentamicin and susceptible to amikacin.