Recent remarkable findings of pharmacogenomics and basic scientific research provided insights in the pathogenesis of severe drug hypersensitivity reactions such as drug rush with eosinophilia and systemic symptoms (DRESS), abacavir hypersensitivity syndrome or blistering reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis). There is increasing evidence for the strong associations of certain human leukocyte antigen (HLA) alleles with hypersensitivity to particular drugs. HLA genes may serve as genomic biomarkers of predisposition to severe adverse drug reactions and enable to prevent them. In this paper we review essentials and advances in this area.