Several factors involved in the etiology of Parkinson's disease (PD) have been proposed, including genetic and environmental factors or even a combination of both. Thus, multiple cellular hits are likely to contribute to neurodegeneration in PD. If such a mechanism happens to occur, our therapeutic intervention may perhaps require a cocktail of molecules acting on various pathways simultaneously. Furthermore, recent evidence suggests that PD may progress even when the initial cause of neurodegeneration has disappeared, suggesting that toxic substances released by the glial cells may be involved in the perpetuation of neuronal degeneration. This may thus represent a therapeutic target for PD.