From September 1979 to August 1981, a total of 25 children with newly diagnosed insulin-dependent diabetes mellitus (IDDM) were admitted for management to the Pediatric Ward, Lubbock General Hospital, Lubbock, Texas. Parents of the 24 admitted patients gave informed consent for their child to participate in the study. While hospitalized, all study patients donated early-phase (acute) blood samples and specimens for virus isolation attempts. Eighteen of the 24 patients originally enrolled in the study continued to come for follow-up visits to the Endocrinology Clinic of the Department of Pediatrics, and hence, provided the late-phase (convalescent) blood samples for the completion of serologic evaluation. The result of this two-year survey is the following: 1) one of the 24 hospitalized cases yielded a non-CB4 enterovirus; (2) serologically, only 2 of 18 IDDM patients showed some CB4 neutralizing antibody (NtAb) activity, ie, rising titers in their late phase sera. In view of the time of onset of patients' symptoms compatible with IDDm, the diabetogenic input of a past CB4 infection could have been considered in one of these two patients. In conclusion, results of our two-year study indicate that occasionally the onset of IDDM might be associated with an acute CB4 infection.