This book details with the Cytotoxic studies and he exploration of essential oils of 26 species belonging to the family Myrtaceae. The were collected from various localities in South india. Of the 26 species 12 members were of the subfamily Leptospermoideae and 14 were of the subfamily Myrtoideae. The cytotoxic potentials of leaf extracts and phytochemical aspects of essential oils were evaluated. The essential oils of these plants belong to 6 distinct classes of chemotypes. 1. Monoterpenoid 2. Sesquiterpenoid 3. Terpenoid 4. Phenolic 5. Mixed and 6. Undetermined. A total of 77 aromatic compounds were detected during the present study. A wide spectrum of cytotoxic, antimicrobial, antifungal , insecticidal, nematicidal, scabicidal , larvicidal and pediculocidal activities were reported for many of these compounds.Hence the crude extracts of leaves of myrtaceaous members either alone or in combination can be used as herbal pesticide. Since many of the myrtaceous leaf extracts leaf extracts show severe mitotic inhibition on onion root tip meristematic cells , they can be effectively exploited as anticarcinogenic agents.