The plasma concentrations of beta-endorphin was determinated by radioimmunoassay in 75 patients with Wetness-Heat Zheng of Liver and Gallbladder, 23 patients with Insufficient Liver Zheng, 13 patients with Insufficient Spleen Zheng and 30 healthy subjects (control group). Compared with the control group, the plasma beta-EP levels were increased in Wetness-Heat Zheng of Liver and Gallbladder and Insufficient Liver Zheng. The patients with different diseases that were diagnosed to be Wetness-Heat Zheng of Liver and Gallbladder presented high levels of plasma beta-EP. It is suggested that the plasma beta-EP is an important change in the syndrome of Wetness-Heat Zheng of Liver and Gallbladder, and may be used as a diagnostic index.