The flavonoid fraction from the leaves of Lantana montevidensis Briq. (Verbenaceae) showed antiproliferative activity against human gastric adenocarcinoma (MK-1, GI50: 12 microg/ml), human uterus carcinoma (HeLa, 5 microg/ml), and murine melanoma (B16F10, 5 microg/ml) cells in vitro.