The pharmacokinetics and bioavailability of famotidine were investigated by HPLC method in 10 Chinese healthy volunteers. Data obtained from HPLC were analysed automatically using a MCPKP program on microcomputer. Linear pharmacokinetics were observed following either iv or po administration. After 20 mg iv, plasma levels declined biexponentially with an initial T1/2 of 0.3 +/- 0.2 h and terminal T1/2 of 3.5 +/- 0.8 h. The plasma elimination T1/2 following po administration were 3.4 +/- 0.7 h and 3.5 +/- 0.5 h for capsules and tablets respectively. Oral absorption was incomplete. The absolute bioavailabilities were 38 +/- 10% for capsules and 43 +/- 11% for tablets. Renal excretion was the major route of elimination. About 72% of the dose were recovered as unchanged famotidine in urine. Mean renal and plasma clearance were 416 and 541 ml.min-1 respectively.