Epidemiological studies link increased garlic (Allium sativum) consumption with a reduced incidence of cancerin various human populations. Experimental carcinogenesis studies in animal models and in cell culture systemsindicate that several allium-derived compounds exhibit inhibitory effects and that the underlying mechanisms mayinvolve apoptosis. To provide a better understanding of the effects of allium derivatives regarding prevention ofcancer, we examined antitumoral activity of allicin, a major component of garlic, in L5178Y lymphoma bearingmice. For in vitro studies, we utilized cell proliferation and apoptosis in the same tumor cell line. We found thatallicin inhibited the growth of tumor cells at doses two fold superior to that in normal splenocytes. Allicin alsoinduced apoptosis, and this was associated with an increase in caspase3 activity.