Kaye, H. S. (CDC, Atlanta, Ga. 30333), H. B. Marsh and W. R. Dowdle. Sero-epidemiologic survey of coronavirus (strain OC 43) related infections in a children's population. Amer J Epid 94: 43–49, 1971.—Acute and convalescent serum pairs and control sera collected from subjects living in a children's home over a 7-year period (1960–1967) were examined by hemagglutination-inhibition (HI) test with coronavirus strain OC 43. Ninety-three serologic conversions were observed; 44 were associated with reported illnesses and 49 with no reported illnesses. In three distinct outbreaks during the winter and spring quarter of 1960–1961, 1964–1965, and 1966–1967, 67 conversions occurred. Seroconversions to strain OC 43 were associated with as much as 19% of the respiratory diseases in a single season. Over the 7-year period coronavirus strain OC 43 accounted for 3% of the total 1328 respiratory illnesses. Evidence of preexisting antibody was apparent in one-third of the children showing seroconversions. The HI test was more sensitive for serodiagnosis than the complement-fixaticn test. The major presenting complaints of the children with respiratory disease associated with coronavirus strain OC 43 were sore throat, cough and coryza; the predominating symptoms were pharyngitis, coryza, fever and cervical adenitis.