A genetic contribution to the etiology of Lewy body Parkinson's disease (PD) is now well established, based on the demonstration of a familial aggregation of the disease by case‐control and twin studies and on the description of large multigenerational families in whom clinically and pathologically typical PD is inherited in an autosomal dominant fashion. In the largest of these families, a gene locus has been mapped to the long arm of chromosome 4 and a putative disease‐causing mutation has been identified in the gene for α‐synuclein. However, analysis of a large number of individuals with sporadic and familial PD suggests that a mutation in this gene is a very rare cause of the disorder, either familial or sporadic. Another locus for autosomal dominantly inherited Lewy body PD has recently been mapped to chromosome 2p13. Possible strategies for the identification of further PD genes are discussed.