Diabetogenic variants of encephalomyocarditis virus, Coxsackievirus B, and reovirus have been studied in vitro in beta cell cultures and in vivo in animal model systems. One of these variants, a Coxsackievirus B4, was isolated from the pancreas of a child who died with acute juvenile-onset diabetes (JOD). The role of the immunologic systems in JOD also is being studied.