A68930, [1R, 3S] 1-aminomethyl-5,6-dihydroxy-3-phenylisochroman HCl, is a potent, partial agonist in the dopamine-sensitive adenylate cyclase model of the D1 dopamine receptor in fish retina. In the rat caudate-putamen model of the D1 dopamine receptor, A68930 is a potent (EC50 2.1 nM) full agonist. In contrast, A68930 is a much weaker (EC50 = 3,920 nM) full agonist in a biochemical model of the D2 dopamine receptor. A68930 also displays weak 2 agonist activity but the molecule is virtually inactive at the 1 and beta-adrenoceptors. When tested in rats bearing a unilateral 6-OHDA lesion of the nigro-neostriatal neurons, A68930 elicits prolonged (> 20 hr) contralateral turning.