Although ethanol has generally not been found to induce cancer in expe
rimental animals, the consumption of alcoholic beverages has been link
ed to increased risks of several cancers in humans. Risks of oral, pha
ryngeal, laryngeal, esophageal, and liver cancer are elevated among dr
inkers, typically in proportion to the amount consumed. Evidence assoc
iating colorectal and breast cancer with alcohol drinking is suggestiv
e but awaits confirmation. All types of alcoholic beverages seem to be
implicated, pointing to an etiological role for ethanol or its metabo
lites. The mechanisms, however, by which alcohol induces cancer in hum
ans are not clear. This review summarizes epidemiological studies of a
lcohol and cancer, focusing primarily on characteristics of the associ
ation that may provide clues to causal pathways.