Growth arrest and DNA damage inducible 45 alpha (GADD45alpha) is a central player in mediating apoptosis induced by a variety of stress stimuli and genotoxic agents. Regular usage of nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin and sulindac is associated with reduced risk for various cancers, including colon cancer. The role of GADD45alpha in NSAID-induced colon cancer cell cytotoxicity is unknown. In this study, we report that indomethacin and sulindac sulfide treatments up-regulate GADD45alpha mRNA expression and protein levels in colon cancer HT-29, RKO and Caco-2 cells. This up-regulation of GADD45alpha is accompanied by necrotic cell death and apoptosis. Anti-sense suppression of GADD45alpha expression inhibited indomethacin and sulindac sulfide-induced necrotic cell death and apoptosis. These findings confirm a role for GADD45alpha in NSAID-induced cytotoxicity, a mechanism for the anti-neoplastic effect of NSAIDs in colon tumorigenesis and cancer growth.