Although acetylcholine and dopamine are believed to play complementary roles in motor function, a comparable neurochemical interaction has not been established for cognitive function. The muscarinic receptor blocker scopolamine and the dopaminergic antagonist haloperidol have been found to impair choice accuracy of rats in the radial-arm maze. In the present study, low doses of these two drugs were administered intraperitoneally either alone or in combination to rats trained on a working memory task (food reward) in an eight-arm radial maze. Scopolamine, 0.125 mg/kg, produced a significant decrease in choice accuracy (i.e., arm entries until an error). Haloperidol, 0.0625 mg/kg, did not cause a significant decrease in accuracy, but there was a trend in that direction. The combination of haloperidol with scopolamine attenuated significantly the amnestic effect of scopolamine. These results suggest that, like motor behavior, cognitive function may be influenced by the balance between acetylcholine and dopamine.