The number of patients of dementia is increasing and has been considered as the serious social problem. In the treatment of dementia, especially in Alzheimer's disease (AD), the acetylcholinesterase inhibitor has been utilized as a first medicine. The inhibitors increases the availability of acetylcholine in central synapse, however the inhibitors cannot reverse the progression nor cure completely. In these circumstances, we focused on the β -secretase inhibitors, which deeply related to the β-amyloid peptide which form senile plaques which said to destroy nerve cells in brain. Thus the longstanding consumption of β -secretase inhibitors in natural plant resources might block the pathogenesis and/or progression of AD. The high sensitive and accurate detection of β -secretase inhibitor has been developed and utilized to screen spices and crude drugs used in the traditional oriental medicines. Among them, then extracts of several spices showed inhibitory activities and their active principle were determined as terpenes and an amine. The strategy for the investigations and the activities of β -secretase inhibitors will be presented in detail.