An increasing body of experimental data supports the role of dopamine as an important neurotransmitter with receptors in both the peripheral and central nervous systems. Previous reports from the authors' laboratories described the unique dopaminergic profile of SK&F 38393 (1, 2,3,4,5-tetrahydro-7,8-dihydroxy-l-phenyl-1H-3-benzazepine). In the first communication, several new 3-benzazepine derivatives are presented, some of which exhibit greatly enhanced specificity and potency in activating renal dopamine receptors while producing little or no activation of central dopamine receptors upon peripheral administration to rats and dogs. The synthesis of these compounds (e.g., 5, 9 [SK&F 82526], 12) is outlined, and their pharmacological properties—including renal vasodilator activity, central dopaminergic effects (e.g., contralateral rotation in lesioned rats, striatal adenylate cyclase stimulation)—are evaluated. Compound 9 emerges as a potent adenylate cyclase-mediated dopamine agonist that does not cross the blood-brain barrier, thus lacking significant central dopaminergic activity. Its potent and specific renal vasodilator effects suggest potential utility in reversing increased renal vascular resistance in hypertensive subjects and managing other disease states characterized by renal ischemia. In the accompanying communication, a novel class of dopamine receptor antagonists and neuroleptics—2,3,4,5-tetrahydro-7,8-dihydroxy-6-(phenylthio)-1H-3-benzazepines (e.g., 1 [SK&F 83742])—is described. These compounds clearly incorporate the structural framework of dopamine within their molecular structure and were identified through studies of SK&F 38393, a potent agonist selective for the D-1 subtype of central dopamine receptors with unique conformational restraints. The synthesis of these 6-(phenylthio)-substituted benzazepines is detailed, and their potential as novel, selective dopamine receptor modulators is discussed.