The pharmacokinetics of ceftibuten, a new oral cephalosporin, has been studied in humans. Ceftibuten is very well observed in young and old patients. Absorption may be slightly decreased by food or relatively high doses (800 mg). The pharmacokinetics have been well characterized in rising single-dose and multiple-dose studies. The half-life is relatively long for this class of drugs, being approximately 2-3 hr. Apparent plasma clearance (CL/F), is approximately 40-75 ml/min, and the renal clearance is approximately 30-50 ml/min, corresponding to the fraction excreted unchanged in the urine of approximately 60%-70% of the dose. The apparent volume of distribution after oral dosing (Vd/F) was approximately 0.2 L/kg. The half-life, plasma clearance, renal clearance, and fraction excreted in urine are not affected by increasing dose and are constant during multiple dosing. There is little drug accumulation during multiple dosing. Drug elimination is decreased in patients with renal insufficiency and dosing in these patients should be adjusted relative to creatinine clearance values. The drug penetrates very well to experimentally induced inflammatory fluid but produces negligible levels in breast milk. The drug has no effect on the pharmacokinetics of theophylline. The drug is well tolerated and has pharmacokinetic properties that are clinically advantageous.