Gossypolis a naturally occurring sesquiterpene chemical and a product of secondary metabolism unique to cotton species. Gossypol is important to the cotton plant because it provides a degree of natural resistance against pests and diseases. Gossypolis the end product of just one branch of sesquiterpene biosynthesis in cotton, with other branches leading to the antibacterial phytoalexins of the Iacinilene group, and the important pest protection chemicals of the heliocides. It and its derivatives are stored in the gossypol glands spread throughout the plant as well as being induced in other tissues when the plants are attacked by disease organisms. Unfortunately gossypol is toxic to humans and monogastric animals, and cottonseed products must undergo expensive post-harvest treatments to remove the high levels of gossypol from oil and meal before consumption. The ideal cotton plant would possess high levels of gossypol in the plant and negligible levels in the seed. This is a characteristic already present in the native Australian cotton species, Gossypium sturtianum, however has proven exceedingly difficult to introgress this trait into cultivated species by traditional breeding methods. Genetic engineering offers another way of producing this phenotype if we have a clear understanding of the enzymes and genes responsible for gossypol production. This project aimed to clone some of the important genes in gossypol biosynthesis and use them in transgenic plants to specifically reduce gossypol production in cotton seeds.