WITHIN recent years increased attention has been paid to the changes in plasma proteins occurring in various disease processes. Such studies by means of electrophoresis1 have yielded interesting and important results and have clearly shown the superiority of this method to the chemical determinations of protein fractions. However, the high cost of apparatus and the technical difficulties restrict the use of this method to relatively few research institutions, whereas a less costly and simpler method would permit investigations on a broader scale. It appears that such methods have been found in plasma chromatography on filter paper2 and in microelectrophoresis.3 This paper deals with the former method. The results of chromatographic investigations of the plasma of 250 patients suffering from various diseases and of 30 normal control persons are given, and the technique of plasma chromatography on filter paper is described. By means of this new procedure it