Genetic predisposition to drug-induced liver injury may be due to variation in both pharmacokinetic and pharmacodynamic pathways. Recent genome-wide association studies have identified, in the human leukocyte antigen (HLA) alleles, strong genetic factors that predispose to liver injury on exposure to any of several drugs. Although the genetic associations have provided mechanistic insights, none has been developed as a predictive test. Further work in this area, in combination with other "-omics" technologies, is needed to develop tests that are both clinically useful and cost-effective.