Objective To explore the effect of Fas and caspase-3 on apoptosis in the white matter damage(WMD) neonatal rats.Methods The pups(45 in each group) were perfused at 30 min,1 h,4 h,12 h,1 d,3 d,7 d,14 d,21 d of recovery from hypoxia-ischemia(HI).Immunohistochemical technique was applied to investigate the changes in the expression of Fas and caspase-3 in periventricular white matter tissues.Apoptotic cells were detected in these tissues by TUNEL.Results Apoptosis index(AI) in the experimental group increased significantly at 4 h and reached the peak at 3 d after HI.No expression of Fas was found in the control group.The expression of Fas in the experimental group appeared at 30 min after HI,increased at 1 h,reached the peak at 12 h and lasted till 3 d.Caspase-3 in the experiment group was up-regulated,peaked at 1 d,demonstrating significant differences at 1 h,4 h,12 h,1 d,3 d and 7 d compared with the control group(P