Huperzine A is a natural cholinesterase inhibitor derived from the Chinese herb Huperzia serrata. There is evidence that huperzine A may compare favorably in symptomatic efficacy to cholinesterase inhibitors in use. In addition, huperzine A has antioxidant and neuroprotective properties that suggest that it may be useful as a disease-modifying treatment for Alzheimer's disease (AD). The drug is available as a nutriceutical in the US. However, there have been no published controlled clinical trials outside China assessing its toxicity and efficacy. This paper reviews the development of huperzine A as a treatment for AD, including the Phase II trial now under way in the US.