This study investigated the cytotoxic effect of ar-turmerone isolated from turmeric (Curcuma longa L) on the K562, L1210, U937 and RBL-2H3 cell lines by the MTT assay. Ar-turmerone exhibited potent cytotoxicity on these cancer cell lines. The IC50 values of ar-turmerone on these cell lines were 20-50 microg/ml. They showed an increased inhibition ratio on cell viability according to the drug concentration < or = 80 microg/ml in the cell lines tested. The DNA fragmentation that is a characteristic of apoptosis due to ar-turmerone occurred in a concentration- and time-dependent manner in the K562, L1210, U937 and RBL-2H3 cancer cell lines. These results suggest that ar-turmerone can induce the apoptotic activity in the K562, L1210, U937 and RBL-2H3 cells.