The success of the phosphotyrosine kinase inhibitor imatinib mesylate (STI571, Gleevec has emphasized the significance of a growing understanding of tumor cell biology. The search has since been intensified to identify other candidate molecules in cancer cell-specific signaling transduction pathways whose disruption may result in similar therapeutic benefits. Flavonoids are potent inhibitors of cyclin-dependent kinases, but in addition also inhibit the activity of angiogenic mediators and induce apoptosis by mechanisms that are still not fully understand. In the current study by Liesveld et al., flavonoids are shown to have an antiproliferative and proapoptotic effect in leukemic cells. The implications of the results of this study on the activity of flavonoids in leukemias and their future development are being discussed.