Huperzine A (HupA), extracted from a club moss (Huperzia serrata), is a sesquiterpene alkaloid and a powerful and reversible inhibitor of acetylcholinesterase (AChE). It has been used in China for centuries for the treatment of swelling, fever and blood disorders. It has demonstrated both memory enhancement in animal and clinical trials and neuroprotective effects. Recently it has undergone double-blind, placebo-controlled clinical trials in patients with Alzheimer's disease (AD), with significant improvements both to cognitive function and the quality of life. Most of the clinical trials are from China, but HupA and derivatives are attracting considerable interest in the West, where AD is a major and growing concern. Furthermore, both animal and human safety evaluations have demonstrated that HupA is devoid of unexpected toxicity. Other interesting aspects of HupA pharmacological profile relate to its neuroprotective properties: it has been shown in animal studies that HupA can be used as a protective agent against organophosphate (OP) intoxication and that it reduces glutamate-induced cell death.