The pharmacokinetics of intravenously administered cefotaxime were studied in 11 patients with creatinine clearances of less than 7 ml/min who were undergoing chronic hemodialysis. Eight were studied during dialysis, and 3 were studied between dialyses. Pharmacokinetic parameters were determined using a two-compartment linear model. The serum half-life of cefotaxime off dialysis ranged from 1.48 to 3.78 hr. The half-life during dialysis was 2.52 \pm 0.34 hr. There was a 28% reduction in serum concentration per hour. A dosage schedule for the use of intravenously administered cefotaxime in patients undergoing hemodialysis is presented.