(R)-SKF-83959 (MCL 202) is enantiomer of D1 receptor agonist SKF-83959. (R)-SKF-83959 is reported to be a functionally selective dopamine D1 and D5 receptors ligand with much lower affinity to dopamine D2 and D3 receptors. (R)-SKF-83959 like SKF-83959, produced dose related effects on overt behavior (eye blinking) and schedule-controlled performance in squirrel monkeys. (R)-SKF-83959 increases in eye blinking and decreases in rates of fixed-ratio responding. In contrast to the effects of its S-(-) enantiomer, was relatively devoid of behavioral activity up to doses that were approximately 10-fold greater than (R)-SKF-83959. Pretreatment with the selective D1- like receptor antagonist SCH 39166 dose-dependently antagonized increases in eye blinking produced by (R)-SKF-83959, confirming the involvement of D1 mechanisms in its effects.