The β-adrenergic agonist 1-isoproterenol (ISO) (10–9–10–7M) provoked a prompt and profound increase of intracellular c-AMP accumulation in monolayer cultures of rat anterior pituitary. In superfused reaggregate cell cultures ISO also stimulated c-AMP outflow. The effect was blocked by propranolol and the highly selective β2-receptor blocker ICI 118.551. Epinephrine (E), norepinephrine (NE) and the highly selective β2-agonist zinterol (ZIN) also stimulated c-AMP accumulation. The order of potency ZIN ≧ E NE together with the high potency of ICI 118.551 suggests the β-effect is mainly through the β2-receptor subtype. The same concentrations of ISO strongly stimulated growth hormone (GH) release and, as previously shown, prolactin (PRL) release from superfused reaggregate cell cultures, but not luteinizing hormone or thyroid stimulating hormone release. Stimulation of PRL and GH release from these cultures was also induced by the adenylyl cyclase activator forskolin. Since interference of β-adrenergic effects on contaminating fibro-blasts or endothelial cells could be reasonably excluded, the present data suggest that β-adrenergic stimulation of c-AMP accumulation in anterior pituitary cells elicits GH a