Continuous hemofiltration is used widely in the management of patients with acute renal failure, but administration guidelines for many drugs have yet to be established. In this study, the pharmacokinetics of ceftriaxone were compared in patients with normal renal function (n = 9), mild renal insufficiency (n = 5), and acute renal failure receiving continuous veno-venous hemofiltration (n = 6). Pharmacokinetic parameters were determined under steady state conditions. Patients with mild renal insufficiency had a significantly lower renal clearance and longer half-life of ceftriaxone; however, drug recovery in the ultrafiltrate with continuous veno-venous hemofiltration was similar to that in the urine of patients with normal renal function. Pharmacokinetic parameters for renal, nonrenal, and systemic clearance and for volume of distribution and half-life were also similar between patients receiving continuous veno-venous hemofiltration and those with normal renal function. The sieving coefficient (S) of ceftriaxone (0.69) significantly exceeded the expected free fraction in plasma, confirming previous reports that protein binding does not limit the sieving of this compound. The results suggest that a reduction in the usual daily dose of ceftriaxone is not required in patients with acute renal failure receiving continuous veno-venous hemofiltration.