Abstract: Fordine, a new alkaloid, was extracted from Chinese herbs Huperziaceae, including Phlegmariurus fordii (Baker) Ching and Huperzia serrata (Thunb.) Trey. It has been shown to inhibit true cholinesterase activity selectively (LD₅₀=3.0 mg/kg ip, 3.6 mg/kg po in mice) and to have therapeutic effect on experimental animal myasthenia gravis.Fordine at doses of 10,40 μg/kg ip or 20 μg/kg po before training caused rapid formation of active avoidance response and significantly increased the active avoidance response in rats. Reversal effect of fordine (10～40 μg/kg ip) against quinuclidinyl benzilate(QNB)800 μg/kg ip induced impairment of active avoidance response was also observed. QNB (30 μg/kg iv)-or anisodine (500 μg/kg iv)-induced EEG changes of rabbits were antagonized with fordine at doses of 20～40 μg/kg iv. Under the same conditions, eserine facilitated the active avoidance response but failed to protect it from QNB. It is suggested that fordine may be a useful compound for improvement of learning and memory.