Parkinson's disease (PD) is a slowly progressive neurodegenerative disorder characterized clinically by bradykinesia, rigidity, tremor, gait dysfunction, and postural instability. Several genes have been identified for monogenic disorders that variably resemble Parkinson's disease. Here, we focus on PARK7, a gene relates to an autosomal recessive form of early-onset Parkinsonism and encodes a protein named DJ-1. Though the exact role of DJ-1 needs to be elucidated, it is generally thought to be functioned as a molecular chaperone and an oxidative sensor (or antioxidative factor). We will review the protective role of DJ-1 to prevent dopaminergic neurons in the substantia nigra pars compacta (SNpc) from degeneration and how its dysfunction would lead to neurodegeneration.