Pharmacokinetic parameters were determined after a single intramuscular injection of 7.5 mg of amikacinjkg to 10 volunteers with impaired renal function (creatinine clearance rate, 2.2–65 mljmin per 1.73 m2) and to six volunteers with normal renal function. The mean peak concentrations of amikacin in sera of the two groups did not differ significantly from each other and exceeded by two to five times the reported in vitro minimal inhibitory concentrations for the majority of Pseudomonas aeruginosa and Enterobacteriaceae strains. There was a significant linear relation between the elimination rate constant of amikacin and the rate of creatinine clearance; there was a significant nonlinear relation between the half-life of amikacin and the serum creatinine concentration. Knowledge of these relations may aid in adjustment of the dosage of amikacin in patients with impaired renal function, especially when such information is used in conjunction with serum assays of amikacin.