Cancer is a group of diseases characterized by cells that grow out of control; in many cases they form masses of cells, or tumors, that infiltrate, crowd out, and destroy normal tissue. Two types of research link alcohol and cancer. Epidemiologic research has shown a dose-dependent association between alcohol consumption and certain types of cancer; as alcohol consumption increases, so does the risk of developing certain cancers. More tenuous results have come from research into the mechanism by which alcohol could contribute to cancer development. The strongest link between alcohol and cancer involves cancers of the upper digestive tract, including the esophagus, the mouth, the pharynx, and the larynx. Less consistent data link alcohol consumption and cancers of the liver, breast, and colon. The epidemiologic data provide little insight into whether or how alcohol increases the risk of various cancers. Studies that have examined direct and indirect mechanisms may show alcohol's role in developing cancers. Preliminary studies show that alcohol may affect cancer development at the genetic level by affecting oncogenes at the initiation and promotion stages of cancer. Although there is no evidence that alcohol itself is a carcinogen, it may act as a cocarcinogen by enhancing the carcinogenic effects of other chemicals. Chronic alcohol abuse may also result in abnormalities in the way the body processes nutrients and may subsequently promote certain types of cancer. 43 references