This volume contains nine more contributions from expert researchers of the field, providing readers with in depth and current research results regarding there spective topics. In the first chapter, Flemming et al. review the chemistry, biosynthesis, metabolism and biological activities of tetrahydrocannabinol and its deritives. Hansch and Verma contribute to the quantitative structure-activity relationship (QSAR) analysis of heterocyclic topoisomerase I and II inhibitors. These inhibitors, known to inhibit either enzyme, actasantitumoragents and are currently used in chemotherapy and in clinicaltrials.