With the use of the spin trapping methods, the scavenging effects of selenite, selenomethionine and seleno-chondoitin sulfate on the active oxygen radicals were studied. We have found that they all had strong scavenging effect on superoxide anions produced by the XOD system and the stimulated polymorphonuclear leukocytes (PMN) and the hydroxyl radical (OH) produced from Fenton reaction as well as an inhibiting effect on the oxygen consumption of PMN during respiratory burst. It is concluded that the different selenium forms can clear the active oxygen radicals produced from both cellular metabolism and chemical reactions.