Objective : Euonymus alatus (Thunb.) Sieb (EA) is a traditional Korean herbal medicine, commonly used to treat tumors in Korea and China for centuries. Several earlier studies have indicated that EA exhibits anti-tumor properties, but its mechanism remains to be elucidated. In this study, we evaluated the molecular mechanism of EA in a human uterine leiomyomal smooth muscle cell (ULSMC) line. Methods : This study was evaluated by: (a), morphological changes by using acridine orange/ethidium bromide staining; (b), DNA fragmentation by TdT-mediated dUTP nick end labeling (TUNEL); and (c), sub-G1 cell analysis. Results : This study observed that EA treatment caused apoptotic cell death and depletion of intracellular glutathione (GSH) and that reduction of mitochondrial membrane potential was found to be involved in the initiation of apoptosis by EA. Conclusion : This results show that EA exerted clear cytotoxic effects and strongly inhibited the proliferation of ULSMC.