A high-performance liquid chromatographic (HPLC) method was developed for biphenyl dimethyl dicarboxylate (DDB) detection in human serum and bioequivalence (BE) of two commercial DDB tablets was evaluated in 14 normal male subjects. The most suitable extracting solvent for DDB in serum was evaluated among dichloromethane, ether, ethylacetate, hexane, and pentane. Pentane:ether (9:1) mixture showed good extraction recovery of DDB from serum and also excluded serum components, which interfere the peak of DDB when assayed. HPLC conditions were as follows: UV absorbance detector, 280 nm; column, μ-Bondapak C