Medical Genetics Summaries (MGS) is an international point-of-care resource for clinicians. It describes the impact that specific DNA sequence variations have on health. The chapters in MGS form a growing collection of peer-reviewed articles that synthesize pharmacogenomic evidence. These articles provide practical information about genetic testing to guide drug therapy and include therapeutic recommendations based on genotype from medical and professional societies. Each chapter is standardized and includes a summary; a description of drug use, metabolism, and action; the enzymatic activity status of significant alleles; the assignment of likely metabolic phenotype based on genotype; and the translation of allele terms used in published literature to terms used in the laboratory, including HGVS expression, star allele, and dbSNP number. Additional MGS articles review genetic variants that underlie inherited conditions or affect the risk of developing a disease in the future. The primary focus of MGS is on genetic variations that influence how an individual may respond to a specific drug.