Considering the MHC implication in modulating the immune or inflammatory processes that characterize psychiatric disorders, we hypothesized that specific alleles, genotypes and haplotypes within the HLA-DQB1 and HLA-DRB1 loci are significantly associated with suicidal behavior, the investigation of these markers leading to the identification of new correlations between HLA polymorphisms and genetic susceptibility to suicidal behavior. This evidence concerns the gene HLA-DRB1 and psychiatric disorder.