P38 mitogen-activated protein kinases (p38 MAPK) and tumor necrosis factor-a (TNF-a) play important roles in oxidative stress-induced apoptosis in cardiac myocytes. However, the regulation and functional role of cross-talk between p38 MAPK and TNF-a pathways have not yet been fully characterized in cardiac myocytes. In this study, we found that inhibition of p38 MAPK with SB-203580 (SB) reduced H 2 O 2 -stimulated secretion of TNF-a, whereas pre-activation of p38 MAPK with sodium arsenite (SA) enhanced H 2 O 2 -stimulated secretion of TNF-a. In addition, pretreatment of cells with TNF-a increased basal and H 2 O 2 -stimulated p38 MAPK and apoptosis of cardiac myocytes, and p38 MAPK-associated apoptosis of cardiac myocytes induced by TNF-a was blocked by inhibition of p38 MAPK with SB. Finally, H 2 O 2 -induced apoptosis was attenuated by the inhibitors of p38 MAPK or reactive oxygen species (ROS), whereas it was enhanced by p38 MAPK agonist SA. These results suggest that H 2 O 2 -induced secretion of TNF-a increases apoptosis of cardiac myocytes through ROS-dependent activation of p38 MAPK. This may represent a novel mechanism that TNF-a partly interplays with p38 MAPK pathways during oxidative stress-modulated apoptosis in cardiac myocytes.