Here we studied whether aspirin (ASA) has any influence on viability of human hepatoma-derived SKHep-1 cells and whether hydrogen peroxide (H 2 O 2 ) has any relation with this effect. ASA inhibited SKHep-1 cell proliferation dose- and time-dependently. Intracellular H 2 O 2 increased as early as 15 min after ASA supplementation. Cellular apoptosis correlated with an increase in intracellular H 2 O 2 level. Moreover, in the presence of a catalase inhibitor-aminotriazol, ASA showed more apoptotic effect on SKHep-1 cells with increasing intracellular H 2 O 2 level. In conclusion, the present results shows that ASA induced SKHep-1 cell apoptosis has a relation with an early increase in intracellular H 2 O 2 level and catalase inhibitor synergizes to induce this process.