Treatment of oral cancers with chemotherapeutic agents become evaluated as an effective method to reduce cancer cell proliferation. Anti-proliferative and anti-oral cancer activities of momordin I on oral cancer cells were evaluated in this study. Momordin I was originally purified from a natural product, Ampelopsis radix and showed the antiproliferative activity against oral carcinoma, KB cells. Obtained $IC_{50}$ value was approximately $10.4{mu}g/ml$. Time-and dose-dependent chromosomal DNA fragmentations were observed in momordin I-treated KB cells. Flow cytometry analysis showed time-dependent apoptotic cell appearance after treatment of momordin I. Approximately 18.6% apoptotic cells were observed at 72 hours after $20{mu}g/ml$ of momordin I treatment. These observation were consistent with the results obtained in DNA fragmentation analysis. These data suggest that momordin I has anti-proliferative effect and induces cell death in KB cells through apoptosis.