Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) have been associated with a reduction in the risk of developing adenomas and colorectal cancer. The available scientific evidence justifies the need for more studies that evaluate the protective effect of aspirin and other NSAIDs as a preventive measure against cancer of the colon; define the minimum efficient dosage; the age at which to begin treatment; the most convenient duration of the latter; and the sub-populations for which the benefits of chemoprophylaxis outweigh possible adverse effects.