A new sesquiterpene, named baccharisketone (1), and a new monoterpene, p-methoxythymol acetate (2), were isolated from the leaves of Baccharis dracunculifolia along with seventeen known compounds (3-19). The structures of the new compounds were determined by spectroscopic means. The growth inhibitory activity of the isolated compounds against leukemia cells (L 1210) was tested and three terpene phenols (4, 6, 17) and five sesquiterpene alcohols (8, 10, 11, 13, 16) were found to exhibit strong cytotoxic activity.