Selenium (Se) is an essential trace element for human health and is associated with a variety of physiological functions. Se, as selenocysteine, is a component of selenoproteins. The most well characterized selenoenzymes is the family of selenium-dependent glutatione peroxides (GSH-px). These enzymes are involved in many biochemical processes such as protection against oxidative stress. Se deficiency results in a significant decrease in GSH-px, and increase in reactive oxygen species production. Inadequate Se level can be linked to increase risk of such disease as rheumatoid arthritis, cardiomyopathy and cancer. The aim of the article was to analyze data referring to the relationship between the selenium level and the risk of rheumatoid arthritis (RA), association of selenium concentration with disease activity and the selenium supplementation effect.