The pharmacokinetics of amoxicillin was investigated in 4 healthy volunteers and in 16 patients with varying degrees of renal impairment, 4 of whom were on regular hemodialysis. Amoxicillin was administered both in a 1-g single intravenous injection and two 500-mg capsules per os. The kinetics of the antibiotic followed an open two-compartment model. In the patients with renal failure there was a significant decrease in beta, kappa10, and total body clearance. A linear relationship between beta of amoxicillin and creatinine clearance was found. This relationship allows dosage regimen adjustment for patients with renal impairment. A significant increase in the absorption half-life of the antibiotic was also observed in patients with renal impairment. The half-life of the antibiotic during hemodialysis was 2.3 h.