Numerous investigations have shown that COX-2 is a participant in the pathway of colon carcinogenesis, especially when mutation of the APC tumor suppressor is the initiating event. Moreover, it seems that the amount of COX-2 is important, since there is a correlation between its level of expression and the size of the tumors and their propensity to invade underlying tissue . Inhibiting COX-2 at an early stage blocks the development of malignant tumors, causes pre-malignant tumors to regress and may improve the outcome once the cancer is completely established. This set of findings seems to link very strongly with the traditional observation that chronic inflammation is a precursor to a variety of types of cancer. By this formulation, inflammatory stimuli increase COX-2 and the downstream events that it induces promote tumor formation. All of these finding suggest that existing NSAIDs will be useful for the prophylaxis of colon cancer and polyps and we eagerly await clinical investigations that will generate guidelines that suggest those individuals that are the most appropriate recipients for such therapy. Although this field has progressed rapidly in the last few years, many important questions remain.