Adenylate cyclase activity was studied on the two epithelial cell types of bovine ciliary process after digestion by trypsin and purification by density gradient centrifugation. cAMP formation after isoproterenol stimulation showed that non pigmented cells were particularly enriched in adenylate cyclase activity. Furthermore pharmacological characteristics of this enzyme indicated that adenylate cyclase-associated beta adrenergic receptors were of beta 2 type in each kind of epithelial cells. These results support the hypothesis that beta adrenergic compounds modulate aqueous humor production through a direct effect on ciliary epithelium and enrichment of beta adrenergic sensitive adenylate cyclase activity in non pigmented epithelial cells suggests that these particular cells may play an important role in aqueous humor secretion.