Our results show a significant association between the C(−1562)T polymorphism in the MMP-9 gene and risk of PD (odds ratio = 2.268, 95% CI 1.506–3.416, p<0.001) as well as risk of sALS (odds ratio = 2.163, 95% CI 1.233–3.796, p = 0.006), supporting a role for MMP-9 polymorphism in the risk for PD and sALS. The gene discussed is MMP9; the disease is Parkinson disease.