PURPOSE: Despite the widespread use of neuroleptic medications for the elderly, little is known about the frequency of treatment for drug-induced parkinsonian syndromes in this age group, particularly with L-dopa-type drugs, which are more appropriate for the treatment of true idiopathic Parkinson's disease. PATIENTS AND METHODS: We identified 3,512 patients aged 65 to 99 enrolled in a large state Medicaid program who were newly prescribed a drug to treat parkinsonian symptoms. Controls were comparable program enrollees of similar age who had not been prescribed an antiparkinsonian drug. In a case-control study, we evaluated the use of neuroleptic drugs in the 90 days before initiation of antiparkinsonian therapy. RESULTS: Patients taking neuroleptics were 5.4 times more likely to begin antiparkinsonian medication than were nonusers (95% confidence interval [CI] 4.8 to 6.1). They also had a greater than two-fold increase in risk of beginning therapy with a dopaminergic drug specific for idiopathic Parkinson's disease, not generally indicated for treatment of drug-induced parkinsonism (adjusted odds ratio 2.2, 95% CI 1.9 to 2.7). Clear dose-response relationships were demonstrated, as were differences among neuroleptics. Among all patients started on dopaminergic drugs in this population, 37% of such therapy was attributable to prior neuroleptic use. Continuation of the neuroleptic persisted in 71% of patients so treated. CONCLUSION: Neuroleptic use is a common cause of extrapyramidal dysfunction in the elderly, and the side effect is frequently treated by adding an anticholinergic or dopaminergic drug to the regimen. The use of anticholinergic drugs presents risks of additional drug side effects; the use of dopaminergic drugs, generally not appropriate for drug-induced parkinsonian syndrome, suggests that extrapyramidal neuroleptic side effects may often be mistaken for idiopathic Parkinson's disease in older patients.