SummaryPatients with sputum-positive pulmoray tuberculosis often display during several months a significant increase in serum transcortin levels. This increase is present before tuberculostatic therapy is started and often disappears before the latter treatment is interrupted. Serum estradiol and hemoglobin Aj£levels were measured in the same blood samples and remained normal. As well withinperson as between-person the transcortin levels did not correlate with the following plasma protein levels or parameters: sedimentation rate, C-reactive protein (CRP), iron binding capacity (IBC), haptoglobin, a,-antitrypsin, a2-macroglobulin, fibrinogen, ceruloplasmin and 5 plasma electrophoretic fractions (albumin, a.<2,/5 and y globulins). On the other hand, the levels of steroid-binding /3 globulin did display changes similar to those observed in the transcortin levels. It remains to be explained why transcortin levels decrease sharply during certain infectious diseases (see reference I) and increase in patients with pulmonary tuberculosis.