Although Parkinson's disease was long considered a nongenetic disorder, it is now clear that there are multiple predisposing genes, and that the disorder can exhibit either Mendelian or non-Mendelian modes of inheritance. The identification of several of these genes has provided important insights into the pathogenesis of this common complex disorder. This article presents an overview of the genes associated with autosomal recessive Parkinson's disease, including Parkin (PARK2), PINK1 (PARK6), DJ1 (PARK7) and ATP13A2 (PARK9). Recently, it was recognized that mutations in the gene encoding glucocerebrosidase, the enzyme deficient in Gaucher disease, are associated with an increased incidence of parkinsonism. While Gaucher disease is an autosomal recessive inherited disorder, patients with Parkinson's disease can be Gaucher heterozygotes or homozygotes. Elucidating the basis for this association may shed light on new disease mechanisms that contribute to the development of parkinsonism.