The largest contribution of type 1 diabetes mellitus (T1DM) from a single locus comes from several genes located in the major histocompatibility complex on chromosome 6p21. Because DQB1 is the best single genetic marker for T1DM, it is the gene most often used to identify individuals with a high risk of developing disease. As per the data collected from the All India Institute of Medical Sciences, among the human leukocyte antigen (HLA)-DRB1 genes, HLA-DR3 showed strongest association with the disease; however, unlike Caucasians and other populations, DR4 was not significantly increased in these patients. HLA-DR10, 11, 13, and 15 showed a negative association with the disease as they were reduced in these patients. In India, the relative risk of developing T1DM is higher with the DR3-DQ2 haplotypes as compared to DR4-DQ8 haplotypes. Studies have shown that in North India, the relative risk for T1DM is comparatively higher (>30) with the DQ2/DQ8 genotype, but is relatively lower (approximately 18) for the DQ2/DQ2 genotype. In addition, the three sets of HLA-B-DR3 haplotypes, mainly B58-DR3, B50-DR3, and B8-DR3 have shown to have modulated susceptibility for T1DM in India and worldwide. New interventions that will be tested in the future will be conducted through T1DM TrialNet, a collaborative network of clinical centers and experts in diabetes and immunology. These studies will identify unaffected first-degree relatives with beta cell autoantibodies who will be eligible for new interventions.