Genetic and biochemical studies have established a central role for alpha-synuclein accumulation in the pathogenesis of Parkinson disease. Here, two microRNAs, namely mir-7 and mir-153, have been identified to regulate alpha-synuclein levels post-transcriptionally. These microRNAs bind specifically to the 3'-untranslated region of alpha-synuclein and down-regulate its mRNA and protein levels, with their effect being additive. They are expressed predominantly in the brain with a pattern that mirrors synuclein expression in different tissues as well as during neuronal development, indicating that they play a tuning role in the amount of alpha-synuclein produced. Overexpression of mir-7 and mir-153 significantly reduces endogenous alpha-synuclein levels, whereas inhibition of mir-7 and mir-153 enhances translation of a luciferase construct bearing the alpha-synuclein 3'-untranslated region in primary neurons. These findings reveal a significant additional mechanism by which alpha-synuclein is regulated and point toward new therapeutic regimes for lowering endogenous alpha-synuclein levels in patients with familial or sporadic Parkinson disease.