text: The isomeric 4-(3-chloro-4-hydroxyphenyl)- and 4-(4-chloro-3-hydroxyphenyl)-1,2,3,4-tetrahydroisoquinolines, the N-methyl derivative of the 4-(4-chloro-3-hydroxyphenyl) isomer, and 4-(3-hydroxyphenyl)-1,2,3,4-tetrahydroisoquinoline were synthesized and evaluated for dopamine D-1 antagonist activity. The 4-(3-chloro-4-hydroxyphenyl) and the 4-(3-hydroxyphenyl) isomer possessed similar potencies as D-1 antagonists. Introduction of the N-methyl group enhanced potency about twofold. The "pharmacophore" for selective dopamine D-1 antagonist activity appears to be a tertiary 2-(3-hydroxyphenyl)-2-phenethylamine.