The endocannabinoids are a family of lipid neurotransmitters that engage the same membrane receptors targeted by tetrahydrocannabinol and that mediate retrograde signal from postsynaptic neurons to presynaptic ones. Discovery of endogenous cannabinoids and studies of the physiological functions of the cannabinoid system in the brain and body are producing a number of important findings about the role of membrane lipids and fatty acids. The role of lipid membranes in the cannabinoid system follows from the fact that the source and supply of endogenous cannabinoids are derived from arachidonic acid. The study of molecules which influence the cannabinoid system in the brain and body is crucial in search of medical preparations with the therapeutic effects of the phytocannabinoids without the negative effects on cognitive function attributed to cannabis. Basic information about function and role of the endocannabinoid system is summarized in the paper; possible therapeutic action of cannabinoids, effects on atherosclerosis specially, is described at the close.