Over the past decade, major progress has been achieved in the identification of genes associated with Parkinson's disease (PD) and parkinsonism. Five genes have now been shown conclusively to play a role in PD susceptibility. Mutations in three of these genes, PRKN, PINK1, and DJ1, are important in early onset, recessively inherited PD, while mutations in LRRK2 and SNCA result in autosomal-dominant PD. LRRK2 has emerged as the most prevalent genetic cause of PD and has been implicated in both familial and sporadic forms of disease. In addition, autosomal-dominant dementia and Parkinsonism has been shown to be caused by mutations in the MAPT and PGRN genes. Molecular tests are now commercially available for several of these genes; however, in some of them, positive results need to be interpreted with caution until penetrance is better understood. In addition, clinical treatment of PD remains largely unaltered by the results of genetic testing.