The high selenium content of the Brazil nut, Bertholletia excelsa, makes this seed a healthy food qualified as an antiradical protector. The studied nut contained 126 ppm of selenium. Selenium was found to be distributed in the nut protein fractions. The water-extracted fraction, which represented 17.7% of the cake protein, was the richest in selenium with 153 ppm. Analysis by HPLC-MS showed that selenium was linked by a covalent bond to two amino acids to form selenomethionine and selenocystine. The selenomethionine represented a little less than 1% of the total amount of methionine.