Physicochemical properties of bergenin, namely the solid state characteristics, solution stability, dissociation constant (pKa), solubility and octanol/water partition coefficient (Log P) were investigated. The results showed that the drug was not hygroscopic and was stable against heat and humidity in the solid state, but sensitive to hydrolysis in the neutral and alkaline solution with a pseudo first-order kinetics. The compound exhibited pKa1 of 5.46 +/- 0.13 and pKa2 of 5.74 +/- 0.18. The solubilities in buffers were slight (e.g. 1.29 +/- 0.044 mg/ml (pH 1.0), 1.08 +/- 0.057 mg/ml (pH 3.0) and 1.22 +/- 0.058 mg/ml (pH 5.0), at 25 degrees C), but increased considerably at high temperatures (e.g. 8.76 +/- 0.039 mg/ml (pH 1.0), 6.75 +/- 0.095 mg/ml (pH 3.0) and 7.80 +/- 0.075 mg/ml (pH 5.0), at 60 degrees C) with chemically stability. The Log P ranged from -1.06 +/- 0.033 to -1.19 +/- 0.044 at pH 1.0-6.0 at 37 degrees C, which demonstrated the poor lipophilicity of bergenin at acidic pHs.