Recent observations have shown that insulin-dependent diabetes (JOD) may be the result of autoimmunity causing more or less rapid pancreatic isle cell destruction. This autoimmune process may be initiated in individuals who are genetically vulnerable to specific virus action. Several viruses have been implicated as causing JOD. Rubella and mumps viruses were the first viruses to be proved diabetogenic. A few years ago Coxsackie B viruses were added to the list. A prospective study of all new diabetics was undertaken in order to clarify the association of viral illness with JOD. 45 new insulin-dependent diabetics were studied (complement fixation, neutralizing antibodies or hemagglutination inhibition) within 3 days following admission. Screening for viral illnesses included the study for antibodies to the following: psittacosis, mycoplasma, Q fever, mumps, measles, herpes, CMV, rubella and chickenpox. Control bloods matched for sex, age, season and year with patients were obtained from individuals screened for viral illnesses during the same period. 18 JOD patients had antibodies against various Coxsackie B viruses. 4 patients had elevated rubella antibody titers.