The severity of side effects that may occur with vitamin K antagonists due to their narrow therapeutic window requires great attention in finding out the most appropriate dose for these drugs. Pharmacogenetic research has now considerably helped clarifying the relationships between genetic variants and sensitivity to such therapy, paving the ground to predictive algorithms that include clinical and genetic variables to establish the best doses to start and maintain an adequate anticoagulation. Pharmacogenetic algorithms indeed aim at identifying tailored regimens, reducing adverse drug reactions and subsequent hospitalizations, optimizing therapeutic efficacy and containing costs. Here we describe the results so far achieved in pharmacogenetic research with vitamin K antagonists, analyzing studies that have assessed the usefulness of such algorithms.