Mammalian tissues contain at least two types of cannabinoid receptor, CB₁, found mainly on neurones and CB₂, found mainly in immune cells. Endogenous ligands for these receptors have also been identified. These endocannabinoids and their receptors constitute the endogenous cannabinoid system. Two cannabinoid receptor agonists, Δ⁹-tetrahydrocannabinol and nabilone, are used clinically as anti-emetics or to boost appetite. Additional therapeutic uses of cannabinoids may include the suppression of some multiple sclerosis and spinal injury symptoms, the management of pain, bronchial asthma and glaucoma, and the prevention of neurotoxicity. There are also potential clinical applications for CB₁ receptor antagonists, in the management of acute schizophrenia and cognitive/memory dysfunctions and as appetite suppressants. Future research is likely to be directed at characterizing the endogenous cannabinoid system more completely, at obtaining more conclusive clinical data about cannabinoids with regard to both beneficial and adverse effects, at developing improved cannabinoid formulations and modes of administration for use in the clinic and at devising clinical strategies for separating out the sought-after effects of CB₁ receptor agonists from their psychotropic and other unwanted effects.