Abstract: A gene-drug specific system for classifying individual genetic variants based on strength-of-evidence of clinical utility from published scientific and clinical data that support their effect on modifying drug response and behavior. This allows categorization of the genetic variants into evidence classes that have a wide range of uses such as pharmacogenomic molecular diagnostics and personalized medicine research designed to guide the clinical implementation of PGx. Furthermore, this information can be combined with a knowledgebase of drug-response phenotypes, a knowlegebase of specific drug-induced outcomes and individual patient diplotype information for a gene-drug combination into a programmed computer to output corresponding patient-specific predicted drug responses.