Cefamandole pharmacokinetics were investigated in 24 adult males with stable renal function and creatinine clearances of 0 to 139 ml/min. After intramuscular injection of 1.0 g of cefamandole, peak plasma concentrations were achieved between 1 and 2 h. Maximum plasma concentration and drug half-life increased as creatinine clearance decreased; i.e., with normal renal function the half-life was 1.49 +&- 0.10 h, and in anephrics the half-life was 11.48 +/- 1.9 h. The greatest increase in half-life occurred when the creatinine clearance was less than 20 ml/min. At these levels of renal impairment, there was significant variance in calculated half-life among patients. The maximum urine concentration and rate of cefamandole urinary excretion decreased as renal function declined. Evidence suggesting renal and nonrenal methods of drug elimination is presented. Hemodialysis resulted in increased cefamandole elimination.