It is generally assumed that parkinsonian patients perceive their need for antiparkinsonian drugs on the basis of emergent motor symptoms. We describe five patients in whom an apparent psychologic effect from levodopa prompted dosage escalation to the point of toxicity. Abstinence from dopaminergic drugs resulted in the appearance of drug-seeking behavior. Psychologic dependence on levodopa has not previously been reported, but appears to occur in a small subset of parkinsonian patients.