The presence of α- and β-adrenergic and muscarinic cholinergic receptors in cerebral microvessels of the rat and pig was assessed by ligand binding techniques. The results demonstrate the presence of specific binding to α2- and β-adrenergic receptors but no appreciable specific binding to α1-adrenergic or muscarinic cholinergic receptors. β-Adrenergic receptors of pig cerebral microvessels are similar to those of the brain and other organs in their binding characteristics to the tritiated ligand and in their stereospecificity of binding to the biologically active isomers of β-adrenergic agonists. Further evidence derived from the differential potency of binding displacement by the various β-adrenergic agonists and selective β1- and β2-adrenergic antagonists indicates that β-adrenergic receptors of pig cerebral microvessels are mostly of the β2-subtype.