Pharmacogenetic research has identified response-related mutant variants in metabolic enzymes and drug-targeted receptors. Allelic variants of dopaminergic and serotonergic receptors have been associated with clinical outcome and adverse events such as movement disorders. Deficient metabolic enzymes have been related to drug accumulation and toxic events. This information will help to design safer and more efficient drugs. However, the field is moving rapidly towards a new goal: the application of pharmacogenetics as a clinical tool for the prediction of treatment outcome. The first studies in this direction have proved the feasibility of using genetic information for the prediction of response to antipsychotic drugs and to treatment of Alzheimer's disease. New strategies investigating genes related to specific symptoms and side-effects have produced encouraging results that can contribute to the improvement of the levels and accuracy of the predictions. This review tries to summarise recent advances and provides an overview of future clinical applications.