AbstractParkinson's disease (PD) is likely due to the combined effects of environment and genes in most cases. Environmental factors inversely associated with PD (or, putative protective factors) include cigarette smoking, use of coffee/caffeine, higher uric acid levels, and anti‐inflammatory drug use. Less well‐established inverse associations with PD include higher cholesterol levels, statin use, higher dietary vitamin B6, and night shift work. Putative risk factors are pesticide exposure, head trauma, certain occupations, and milk consumption. The pathogenesis of PD may begin decades before motor symptoms. PD may have shared determinants with other neurodegenerative disorders involving abnormal protein aggregation. © 2010 Movement Disorder Society