Pharmacokinetics of arbekacin (HBK), a new aminoglycoside, was studied. Serum concentrations and urinary excretion were determined after single intravenous drip infusion of 100 mg HBK for 1 hour to healthy volunteers and patients with renal insufficiency of various kinds. The drug concentration was determined with bioassay, fluorescence polarization immunoassay (FPIA) and high-performance liquid chromatography (HPLC). Pharmacokinetic analysis was made in accordance with the two-compartment open model, and 24-hour endogenous creatinine clearance (Ccr) was used as the renal function index. In all cases peak serum levels were detected 1 hour after administration, and similar values were noted regardless of subjects' proficiencies of renal function. However, the serum clearance during beta-phase tended to be prolonged parallel with the degree of renal insufficiency. The excretion of HBK into urine was prolonged and cumulative recovery tended to be decreased in association with the decreased valued of Ccr.