The pharmacokinetics of a new aminoglycoside, amikacin, was evaluated in 37 infants between 1 and 34 days old. Fifteen were below 2,500 gm in weight. Initial studies, including intravenous infusion in some of the infants, indicated that the disposition of amikacin was best described by a 2 compartment model. The absorption was evaluated in 8 of the infants after intramuscular injection of 7.5 mg amikacin per kilogram of body weight. The absorption rate, estimated by the tmax, was significantly faster than reported in adults. The total body clearance and apparent volume of distribution were studied in 22 infants after the same dose of amikacin intramuscularly. The body clearance expressed in relation to body surface or body weight was significantly less than in adults and correlated with the postnatal age. No correlation could be demonstrated between clearance and gestational age or birth weight. The volume of distribution per kilogram was significantly greater than in adults. On the basis of the derived kinetic parameters, a dose schedule is presented. In 5 children there was a reasonable agreement between the measured and predicted serum levels.