Adding to earlier reports on HLA associations of truncated GAD autoantibodies (8), the current study reports at least 2 new findings: (1) the higher frequency of t-GADA in individuals carrying the DR4-DQ8/x genotype and specifically the DRB1*04:04 allele in the DR4-DQ8 haplotype compared with those carrying the DRB1*04:01 allele in this haplotype and (2) the higher frequency of M-epitope–specific GADA among individuals positive for the haplotypes confering the highest HLA risk for T1D (DR4-DQ8 and DR3-DQ2) relative to those without such haplotypes. Here, GAD1 is linked to type 1 diabetes mellitus.