Depression is commonly associated with idiopathic Parkinson's disease. Various antidepressants can be helpful in the treatment of this type of depression. Anticholinergic medications are at times used for treating the motor symptoms of parkinsonism. While some authors have reported euphorigenic effects from anticholinergics in other groups of patients, generally, they have not been used in the treatment of depression, with or without parkinsonism. In the case presented, a depressed patient with Parkinson's disease on levodopa/carbidopa and fluoxetine was given benztropine for his motor symptoms. The result was some improvement in his motor symptoms and a wide, dose-related spectrum of other central nervous system changes ranging from delirium to mania, hypomania, and euthymia from a "baseline" of residual depression. At a very low dose (0.25 mg per day), benztropine appeared to have an augmenting antidepressant effect that rendered the patient euthymic.