The terpenoids are the largest known class of natural products, with over 20,000 reported structures. Ginger (Zingiber officinale Rosc.) and turmeric (Curcuma longa L.), most well known for their anti-inflammatory activities, each produce an array of bioactive mono- and sesquiterpenoids in their tissues. For example, ar-turmerone, one of the major turmeric sesquiterpenoids, has been shown to selectively induce apoptosis in human leukemia cell lines, Molt 4B and HL-60, but not in human stomach cancer KATO III cells. Based on its structure, we can predict that ar-turmerone may be synthesized in the plant from sesquiphellandrene via curlone. To assist in our efforts to elucidate the biochemical pathways to the most important bioactive constituents of ginger and turmeric, we produced an EST database from 8 cDNA libraries from rhizome, root, and leaf tissues of these plants. In this database of over 50,000 ESTs, 45 contigs (111 ESTs) appear to be terpene synthases (TPSs): 19 monoterpene, 11 sesquiterpene, 2 diterpene, 3 triterpene and 10 tetraterpene synthases. We have begun to characterize the corresponding recombinant TPS proteins by expressing them in E. coli, incubating with GPP (geranyl diphosphate, precursor of monoterpenes) and FPP (farnesyl diphosphate, precursor of sesquiterpenes) and analyzing the products by GC/MS. So far we have identified a monoterpene synthase that produces cineole from GPP, and a sesquiterpene synthase that produces nerolidol from FPP and linalool from GPP. We are continuing our investigation of the rest of the candidate TPS genes. Progress in identification of these enzymes will be discussed.