The search for genetic mutations responsible for familial forms of Parkinson's disease (PD) has identified several genes and loci. Mutations in the parkin gene are linked to autosomal recessive juvenile parkinsonism. The genetic forms of PD are uncommon, but gene therapy targeting alpha-synuclein, parkin, or other pathways may be also applicable for idiopathic PD. Intriguingly, several studies suggest that parkin gene therapy could be useful in a subset of PD patients with mutations in the alpha-synuclein gene. Furthermore, if parkin overexpression can correct neuronal degeneration in the substantia nigra and striatum, it might be a potentially effective therapy for alpha-synucleinopathy.