Abstract The distribution of selenium (Se) in human plasma proteins was studied by gel filtration chromatography (Sephacryl HR 200). In addition to glutathione peroxidase (GSHPx), two selenium peaks were noted in unequal proportions (A: 65–75%, B: 25–35%). 200 μg of 74Se-selenite were given orally to healthy subjects, and the distribution of 74Se was followed at 1,4, 6, 8, 12, and 24 hours after labeling. No labeling of red blood cells was found. No modification of plasma GSHPx activity was observed for 24 hours. The two selenium peaks were investigated and the 74Se enrichment was determined. We observed a maximum enrichment for peak A at 12 hours and for peak B at 4 hours.