We evaluated the antitumor activity of the Bax gene and green fluorescent protein/tumor necrosis factor-related apoptosis-inducing ligand (GFP/TRAIL) fusion gene driven by the human telomerase reverse transcriptase promoter both separately and combined in the human ovarian cancer lines SKOV3ip and DOV13 and human lung cancer line H1299. In vitro study showed that both TRAIL- and Bax-expressing vectors elicited significant cell killing in H1299 and SKOV3ip cells, but only the GFP/TRAIL gene elicited significant cell killing in DOV13 cells. Combined TRAIL and Bax therapy also produced more profound cell killing in SKOV3ip and H1299 cells, but not DOV13 cells without escalation of the vector doses. To further evaluate the combined effects of Bax and TRAIL, abdominally spread tumors were established in nude mice via intraperitoneal inoculation of SKOV3ip cells followed by that of adenoviral vectors. Tumor growth, ascites formation, survival duration and toxicity were evaluated after treatment. We found that treatment using the Bax- or TRAIL-expressing vector alone significantly suppressed tumor growth and ascites formation, and prolonged animal survival when compared with that of using PBS or a control vector. Combined TRAIL and Bax therapy further prolonged survival significantly when compared with therapy using the TRAIL or Bax gene alone. Transgene expression and apoptosis induction were not detected in normal human ovarian epithelial cells in vitro or normal mouse tissues in vivo after intraperitoneal vector administration. Also, liver toxicity was not detected after either treatment. Thus, combined TRAIL and Bax gene therapy may be useful for treatment of abdominally spread tumors.