In this chapter an overview of the more recent developments in the structure-activity relationships (SARs) of classical cannabinoids is discussed, especially the profound pharmacological effects produced by various chemical entities in the side chain at C-3, the hydroxyl at C-1, C-11, and hydroxyalkyl chains at C-6. Also cardiovascular studies point to the presence of a novel cannabinoid subtype receptor and the antagonist activity of cannabidiol has opened up new areas for research. Ligands, which had either a unique pharmacological profile, were potent agonists, partial agonists/antagonists, or were CB2 selective, were identified, generating leads with the potential to be drugs in the treatment of various diseases.