To establish an HPLC-MS/MS method for the determination of adefovir in the plasma, and to evaluate the bioavailability of adefovir dipivoxil capsules and tablets in Chinese healthy male volunteers.With aciclovir as the internal standard, the plasma samples were processed with methanol precipitation and analyzed by HPLC-MS/MS on a Hedera ODS-2 C18 (150 mm × 2.1 mm, 5 μm).A cross over bioequivalence trial was designed and 18 Chinese healthy male volunteers were divided into 2 groups.Each group was orally given adefovir dipivoxil capsules or tablets 10 mg.The pharmacokinetic parameters and relative bioavailability were calculated to evaluate the bioequivalence of the two preparationsThe calibration curve was linear within 0.5-100 ng·mL-1 (r=0.9986).The extraction recovery of adefovir was 71.2%-72.8% (n=5), and the intra-day and inter-day RSD was 4.3%-7.7% (n=5) and 2.9%-8.0% (n=15), resp.The AUC0-t of capsules and tablets was (416.0±106.8) and (410.8±105.9) ng·h·mL-1, AUC0-∞ (425.5±107.1) and (422.1±106.5) ng·h·mL-1, Cmax (35.23±9.6) and (34.31±8.6) ng·mL-1, tmax (1.7±0.5) and (1.6±0.8) h, and t1/2 (8.1±1.2) and (8.5±1.3) h.The relative bioavailability of adefovir dipivoxil capsules to the reference tablets was (103.7±24.5)%.The established HPLC-MS/MS method was accurate and sensible.It could be used to study the pharmacokinetics of adefovir in human plasma.The two preparations were bioequivalent.