AIM: To investigate the possible role of nuclear transcription factor kappa B (NF-?B), Bcl-2, Bax and caspase-3 in etodolac-induced apoptosis of liver tumor SMMC7721 cell line. METHODS: Cell apoptosis was determined by flow cytometry analysis with PI staining and DNA laddering. Expression of Bcl-2 and Bax protein was measured by Western blotting. Caspase-3 activity was evaluated by active caspase-3 apoptosis kit with flow cytometry. NF-?B activation was detected by ELISA-based TransAM~(TM) NF-?B p65/p50 kit. RESULTS: Etodolac, a selective COX-2 inhibitor, stimulated apoptosis in liver tumor SMMC7721 cell line significantly. Flow cytometry showed that the apoptotic rate was 16.3%?3.1%, 19.9%?3.6%, 22.9%?3.2%, 31.2%?3.3% with different concentrations of etodolac (0.25, 0.50, 1.0 or 2.0 mmol/L), while the apoptotic peak did not appear in the control group (0 mmol/L) (P