National Prohibition in the USA (1919-1933) was followed by an era in which medical scientists played an important role in minimizing the harmful effects of alcohol. Cirrhosis, cardiomyopathy, adverse fetal effects, and esophageal cancer are examples of alcohol-related health problems that were well known at the beginning of the 20th century but were dismissed during the late 1930's and early 1940's, only to be rediscovered during the 1960's and afterwards. This eclipse in knowledge occurred because of skepticism about earlier claims that had been made in the name of scientific temperance and, most importantly, because of changing standards for medical evidence. The paradigm for disease causation that gave birth to modern medicine was based on microbiology and reinforced by hormone and nutrition discoveries. Most alcohol-related health problems are poorly explained by this paradigm. The more recent epidemiologic paradigm for noninfectious disease is more applicable to the health risks associated with heavy drinking. A transformation of knowledge about alcohol's relationship to disease has occurred.