Evidence for the human carcinogenic effects of alcohol consumption on the risk of cancers of the oral cavity and pharynx has been considered sufficient in the International Agency for Research on Cancer Monograph 44 on alcohol and cancer in 1988. We evaluated human carcinogenic evidence related to the risk of oral and pharyngeal cancers based on cohort and case-control studies published from 1988 to 2009. A large body of evidence from epidemiological studies of different designs and conducted in different populations has consistently supported the fact that alcohol consumption is strongly associated with an increase in the risk of oral and pharyngeal cancers. The relative risks are 3.2-9.2 for more than 60 g/day (or more than four drinks/day) when adjusted for tobacco smoking and other potential confounders. A strong dose-response effect on the intensity of alcohol use is reported in most of the studies. However, no apparent association is observed for the duration of alcohol use. Compared with current alcoholics, a decreased risk of approximately 10 to 15 years is associated with alcohol cessation. Similar associations have been observed among nonsmokers in over 20 studies. In general, the dominant type of alcohol consumption in each population is associated with the greatest increase in risk. A large number of studies on joint exposure to alcohol and tobacco consumption show a greater than multiplicative synergistic effect.