Objective: To explore the significance and effect of apoptosis in the development of cleft palate induced by dexamethasone (DEX). Methods: Various doses of DEX (10-50 mg/kg) were injected intraperitoneally into Kunming mice on gestation day (GD) 12. The cranio-maxillary sections of samples were labled by HRP-avidin-biotin-dUTP in situ end-labeling (ISEL) and were observed morphologically and quantitatively under a light microscope and electron microscope. Results: ISEL positive cells were found in treatment groups. The means of sums and cleft palate incidence have a positive correlation with the doses of DEX (r = 0.9911/0.9978). Conclusion: A relationship exists between an increased level of apoptosis and the development of cleft palate induced by DEX.