To be included in the study, an affected sibpair (ASP) family had to have at least one ASP available for sampling; availability of one or both biological parents; and the same source (blood or cell line) of DNA for all family members. For parent-offspring trio families, all three members (both paretns and the T1D-affected offspring was required to have the same source of DNA (blood or cell line). An individual was designated as affected with type 1 diabetes (T1D) if he or she had documented T1D with onset at <35 years of age, had used insulin within 6 months of diagnosis, and had no concomitant disease or disorder associated with diabetes. Preference was given to those families having participants with ImmnoChip genotyping.