The role of the ocular autonomic nervous system in IOP regulation has been well established. Pharmacological and autohistoradiographic studies confirmed the high density of beta 2 and alpha 2 receptors on ciliary processes and iris epithelium. Their respective pharmacological activation or blockade is discussed. The role of other ocular neurotransmitters is also complex, as shown by the paradoxical similar action of dopamine agonists and antagonists on IOP. Concerning the cholinergic system, ocular muscarinic receptors are pharmacologically not well documented. Numerous other neurotransmitters may modulate IOP without necessarily leading to the development of new drugs. Drugs of the future will probably concentrate on dopaminergic agonists, cAMP-stimulators such as forskolin, prostaglandins, and cannabinoids.