INFECTION does not always result in disease or illness. Only a proportion of infected persons become sick following many epidemic and endemic infections. Social, economic, racial, and other factors obviously influence the frequency of infection and disease in a population, affecting the degree of exposure to the microorganisms and natural resistance. The impact of psychological factors upon the frequency of infection and infectious disease, however, has not been previously evaluated. The onset or exacerbation of disease during a chronic infection, such as tuberculosis, may be partly dependent upon antecedent emotional stresses.1 Development of illness with acute infection, however, has not been related to psychological factors. The severity of acute infection as measured, for example, by the height and duration of fever, has not been shown to be influenced by emotional factors,2,3 but psychological stresses might magnify the symptoms of illness. Delayed recovery from symptoms associated with infection