13 patients with PD of recent onset underwent a series of neuropsychological tests for frontal lobe associated functions (Sternberg paradigm, WCST, CVLT) before and during treatment with Artane. Test results at baseline were not significantly different from those of an age-matched control group (n = 13). Retesting after a mean of 2 weeks' treatment with trihexyphenidyl revealed only slight impairment in CVLT while performance on the other tests remained unchanged.