Therefore, we deduced that the concentrations of ROS, MDA, T-SOD, CAT, and GSH-Px were implicated in the development of AD and that EGb played its neuroprotective roles by increasing the expression of T-SOD, CAT, and GSH-Px or by decreasing both ROS and MDA to exert a direct free radical scavenging effect. The gene discussed is CAT; the disease is Alzheimer disease.