Erythromycin pharmacokinetics were examined following intravenous infusion to male subjects. The biological half-life of erythromycin in serum was 2 hr in individuals with normal renal function. The half-life varied in cases of reduced renal function, with values of 3.9 and 7.0 hr occurring in two subjects with severe renal impairment. Postinfusion serum erythromycin levels were adequately described by two-compartment model kinetics, and values for the distribution volume of the central compartment and the overall distribution are described. Estimated erythromycin distribution volumes in normal individuals may facilitate calculation of absorption efficiencies of erythromycin and its salts after oral doses.