Selenium is an essential trace element. In the form of selenocysteine, an amino acid, selenium is necessary for the activity of important enzymes (i.e. glutathione peroxidases, thioredoxin reductase). In the periodic table of the elements, selenium belongs to the same column as oxygen. In fact, seleno-enzymes have an important role in the detoxification of reactive oxygen species, especially peroxides and hydroperoxides. In septic and septic-like shock patients, reactive oxygen species, particularly peroxides, play an important role through their destructive actions, which are favourable as critical components of microbial destruction and also deleterious in excessive generation. This excessive generation results in tissue damage. Moreover, reactive oxygen species modulate the activation of important intracellular mediators (NF kappa B activation, arachidonic acid cascade). Simultaneously in patients with severe infection, there is a marked and early plasma selenium decrease. Redistribution due to selective selenium uptake for metabolic use could be one of the main mechanisms for this decrease. This review was carried out by questioning on the one hand the Medline database, by consulting the reviews and works available in the services of biology, biochemistry and pharmacy, by a prospective follow-up on the subject in Current Contents, but also thanks to library searches carried out by Aguettant laboratories. Several supplementary studies at various doses (from 140 to 1000 micrograms/day sodium selenite) have been conducted, though only on small groups of patients and with a questionable design. Selenium treatment seem to be promising in severely septic patients. However, in the absence of pertinent clinical data, only the administration of doses below adverse effect levels, staying within physiological limits, can presently be recommended (i.e. 200 to 500 micrograms/day of sodium selenite).