Much hope is currently associated with individualization of therapy provided to rheumatoid arthritis (RA) patients. The search is underway for biochemical and clinical markers that would be useful in prediction of a good response to methotrexate (MTX) therapy. Along with clinical factors, genetic predisposition may also be helpful. Polymorphism of genes participating in MTX metabolism may affect the drug’s efficacy and the rate of adverse effects. Pharmacogenetic studies may contribute to more effective individualization of therapy for RA patients. The purpose of the study was to determine the significance of gene polymorphisms MTHFR C677T and A1298C for efficacy of MTX therapy in RA patients. Patients possessing determined polymorphisms should be particularly carefully evaluated because of a higher risk of occurrence of adverse effects.