Investigation was made on absorption, excretion and clinical responses following intravenous drip infusion of amikacin (AMK) and the following results were obtained. 1) Serum concentrations of AMK were determined after completion of a 1 hour-course of its intravenous drip infusion at a dose of 200 mg, involving 2 patients with normal renal function and 1 patient with impaired renal function. In the patients with normal renal function, a mean peak serum concentration of 15.9 micrograms/ml was reached at the termination of the intravenous drip infusion and, then, gradually declined to 0.97 microgram/ml at 6 hours after completion of the intravenous drip infusion. The half-lives were 1.64 and 1.41 hours, respectively. In the patients with impaired renal function, the elimination of AMK from blood flow was markedly delayed and the serum concentration was 5.52 micrograms/ml even at 6 hours after completion of the intravenous drip infusion. The half-life was prolonged, its value being 5.98 hours. 2) The mean urinary excretion rate for the patients with normal renal function was 67.7% within 7 hours, while the patient with impaired renal function had a lower rate of 14.0%. 3) Ten infectious patients with hematological malignant diseases were treated with AMK intravenous drip infusion. Clinical responses were excellent in 6, good in 2, fair in 1 and poor in 1. Thus, 80% of the patients responded to AMK. 4) In order to check the side effects of AMK, investigation was made on the results of various clinical laboratory tests and the subjective and objective findings. But, no side effects attributed to AMK were observed. Therefore, it is thought that the intravenous drip infusion of AMK will be very useful when attention is paid to infusion time, dose and interval.