An endogenous compound that binds to the same receptor sites activated by the main psychoactive constituent of marihuana, delta 9 tetrahydrocannabinol (THC), is synthetised in the brain and in several peripheral tissues. The endogenous cannabinoid was named anandamide on the basis of the sanscrit word ananda, that means bringer of inner bliss . Anandamide reproduces marihuana effects,is synthetised in response to physical activity, and is involved in neurobiologic mechanisms common to drug addiction. Cannabinoid CB1 receptors, and their endogenous ligands, are present in brain areas linked to reward circuits. The blockade of CB1 receptors causes anorexia and is being employed to treat obesity. On the contrary, activation of CB1 receptors has appetite stimulant, antiemetic and analgesic properties, that deserve to be studied for putative therapeutical uses.