Rheumatoid arthritis (RA) is a systemic, chronic and inflammatory disease of unknown etiology. HLA-DRB1 and PTPN22 1858T gene variants are risk factors of RA, clinical manifestations and rate of progression of joint destruction in this autoimmune disease. Currently, several immunopathogenetic models of other genes (CTLA4, MIF, PADI4 and SLC22A4) are under debate. The clinical influence of some of the gene polymorphisms associated with RA and the principles of pharmacogenetics applied to different therapies, such as classical disease-modifying anti-rheumatic drugs and new biological agents. Pharmacogenetics is a rapidly advancing area of research that holds the promise that therapies will soon be tailored to an individual patient's genetic profile.