To examine evidence of a causal link between handwashing and risk of infection, a review of published literature from 1879 through 1986 was conducted. In the 107 years studied, 423 articles specifically related to handwashing were found. Articles were categorized as studies to evaluate products (50.8%), review articles (29.1%), behavioral studies (10.9%), methodologic studies (2.8%), studies linking handwashing to infection (3.3%), and other (3.1%). There was an increase in the proportion of handwashing articles published in the 1980s with the rate (9.4/10(5) citations/year) being almost double that of any other period studied. Nonexperimental and experimental studies related to handwashing were reviewed and evidence for a causal association evaluated. Except for specificity, all the elements for causality, including temporality, strength, plausibility, consistency of the association, and dose response were present. It was therefore concluded that emphasis on handwashing as a primary infection control measure has not been misplaced and should continue.