OBJECTIVE: To investigate associations between statin (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor) use and Parkinson disease (PD). METHODS: We used a population-based design to recruit 312 incident idiopathic PD cases and 342 controls from three rural California counties. RESULTS: We observed a higher frequency of statin use among controls vs cases (OR 0.45; 95% CI 0.29 to 0.71) and a strong dose-response relation. The strongest protective association between statin use and PD was observed in long-term (>or=5 years) users (OR 0.37; 95% CI 0.18 to 0.78). There was no difference by gender or age. We noted 60 to 70% risk reductions for each individual statin except pravastatin. CONCLUSION: Ascribing causality to these associations is premature and further studies are needed to confirm a potential neuroprotective role for statins in PD.