Case records of 1,098 patients treated with amikacin at 79 research centers in 10 countries in a program of worldwide clinical trials were reviewed. Of the 697 patients eligible for use in evaluation of efficacy of the drug, 81% were cured, as evidenced by clinical remission and eradication of the infecting pathogen. The usual dosage was 7.5 mg/kg administered intramuscularly at 12-hr intervals. This dosage was modified in patients with renal impairment. Amikacin was effective in 90% of 322 patients with genitourinary infections, 85% of 97 patients with septicemia, 70% of 73 patients with infections of skin, soft tissue, or bone (excluding burns), and 69% of 68 patients with infections of the lower respiratory tract. Amikacin was effective in treatment of 88% of 85 infections due to gentamicin-resistant pathogens. The drug was generally well tolerated, and no side effects were reported in 80.6% of the 1,098 patients evaluated. Amikacin shares with other aminoglycosides the risk of ototoxicity and nephtotoxicity; previous exposure to gentamicin was a major factor in the development of such adverse effects. Other adverse reactions were relatively infrequent and in most cases were characterized as mild and transient.