Publisher Summary This chapter discusses cannabinoid drugs. Because of its psychotropic properties, Cannabis sativa was one of the first plants to be used by man, both in social-religious rites and in medicine. Many of the actions produced by Cannabis are undoubtedly distinct from the placebo effect, and in recent years, some have been confirmed in animals and in man. The chapter compares past use with modern data to present an overview of modern use and developments and to predict future pathways in medicinal chemistry research in this area. The following abbreviations are used: THC (tetrahydrocannabinol), CBD (cannabidiol), CBN (cannabinol), DMH (1,l-dimethylheptyl), SAR (structure–activity relationship), cisplatin (cis-diamminedichloroplatinum(II)), GABA (γ-aminobutyric acid), MES (maximal electroshock seizures), PTZ (pentylenetetrazol), AGS (audiogenic seizure), IOP (intraocular pressure). It is probably impossible for man today to comprehend fully the attitudes of an ancient population toward drugs and their associations with beliefs, religion, superstitions, and social life and interactions. Cannabis oil and leaf juice were employed externally for various skin diseases, wounds, and even in leprosy. The topical antibiotic properties of cannabinoids as known today justify the use in appropriate skin diseases. Cannabis was also used against vomiting. This use was widespread in India as well.