The variation, in heaIth and disease, of the a,-lipoproteins, or at least of lipids in the electrophoretic albumin-a, region, has received fairly wide attention (for references see Lindgren & Nichols l% o). The electrophoretic al-lipopwtein fraction migrates faster and spreads more, widely than most of the other components. Its electrophoretic behavior also varies with the duration of storage of the serum and with variations of the intermediary lipid metabolism. It is the heaviest normal al-component (about 300 mg per 100 ml) calculated as protein, but it is electrophoretically heterogenous and does not give rise to any well demarcated electrophoretic protein peak, which is evident on comparison of the paper and agar gel electrophoretic patterns after staining for lipids and proteins. The orosomucoid, which normally occurs in a concentration of about

75 mg per 100 ml (Goodman, Ramsey, Simpson & Brennan 1957) produces no demonstrable peak on paper or in agar gel electrophoresis, because it is partly masked by the slower part of the albumin fraction, and it stains only faintly with bromphenol blue (Sundblad & Wallin-Nilsson 1962). The alx component normally occurs in a concentration of about 30 mg per 100 ml (Schultze, Heide & Haupt 1% 2), which is not high enough to produce a distinct peak on paper electrophoresis. Burtin (1960) has stated that the strongly antigenic 3.5 S a,-glycoprotein (a1*, al-antitrypsin) is the dominating normal a, tomponent. We have accepted this concept for two reasons. The precipitation maximum of the line formed by anti-a,-antitrypsin corresponds to the a,-protein peak obtained on paper and agar gel electrophoresis with different buffers. It may be deduced from data given by Jacobson (1955) on the a,-antitrypsin activity that if the molecular weight of the a,-antitrypsin is about 6Oo00, the mean normal concentration will be 0.18 g