Parkinson's disease (PD) is a neurodegenerative disorder affecting a significant proportion of the ageing population. The etiology is unknown and it is likely due to a multifactorial interaction of genes and the environment on the background of ageing. Findings in the last decade suggest that the contribution of genetics to familial forms of PD is much greater than previously appreciated. Twelve loci are now associated with highly penetrant autosomal dominant or recessive PD, and causative mutations have been identified in eight genes with mutation carriers often characterized by a phenotype indistinguishable from idiopathic disease. To date, PD pharmacotherapy is symptomatic only and does not slow disease progression. Understanding how genetic mutations cause familial PD is likely to clarify molecular mechanisms underlying PD in general and will provide a guide for the development of novel therapies, both preventative and palliative, applicable to all forms of parkinsonism. This review outlines the advances in the study of the genetic background of PD and their possible clinical implications.