DISTINCT EFFECTS: Since the discovery of the two isoforms of COX, the therapeutic effects of nonsteroidal antiinflammatory drugs (NSAID) can be distinguished from their adverse effects linked to the inhibition of the constitutional form via selective inhibition of the inducible form. Non-selective NSAID that inhibit both COX isoforms are difficult to use for long-term regimens. NSAID AND CANCER PREVENTION: Epidemiology studies and animal and in vitro studies have demonstrated that regular use of NSAID reduced the incidence of colorectal cancer and certain precancer lesions. PROMISING PERSPECTIVES: COX-2 specific inhibitors, for example cerecoxib or rofecoxib, are potentially interesting for human therapy for chemoprevention of epithelial cancer or as medical treatment, alone or in combination with other anticancer treatments.