To investigate the role of activation of c-Jun NH2-terminal kinase 1 (JNK1) in mediating cisplatin-induced apoptosis and the possibility of induction of JNK activity in triggering relation to DNA damage and drug resistance. We investigated the difference of cisplatin-induced activation of JNK pathway and H2O2 alteration between cisplatin-sensitive human ovarian carcinoma cell line A2780 and its resistant variant A2780/DDP. JNK, p-JNK protein, and extracellular H2O2 levels were determined in both A2780 and A2780/DDP cells which were transfected with dominant negative allele of JNK and recombinant JNK1 separately. Both A2780 and A2780/DDP were treated with CDDP, the JNK pathway was activated and a prolonged JNK activation was maintained for at least 12 h in A2780, and only a transient activation (3 h) was detected in A2780/DDP in response to cisplatin treatment. Inhibition of JNK activity by transfection with a dominant negative allele of JNK blocked CDDP-induced apoptosis significantly in A2780 cells. Selective stimulation of the JNK pathway by lipofectamine-mediated delivery of recombinant JNK1 led to activation of c-Jun and decrease of extracellular H2O2, as well as apoptosis sensitization to CDDP in A2780/DDP cells. We concluded that JNK pathway might play an important role in mediating cisplatin-induced apoptosis in A2780 cells, and the duration of JNK activation might be critical in determining whether cells survive or undergo apoptosis. The resistance to CDDP can be reversed through activating c-Jun and decreasing extracellular generation of H2O2 by pcDNA3(FLAG)-JNK1-wt transfection in A2780/DDP cells.