The author executed the tuberculin reaction and the paperelectrophoresis of the lung tuberculosis patients after pulmonectomy and also the paperelectrophoresis of the patients' sera, and obtained the following results. 1. Of 16 tuberculosis patients 9 cases (56.2%) showed the weakening in the tuberculin reaction after pulmonectomy, and 5 cases (31.2%) showed a transient weakening of the reaction but a later recovery. 2. When the aqueous solution of old tuberculin is used in the dilution of 1:100, 1:2, 000, and 1:10, 000, the tuberculin reaction after pulmonectomy shows a weakening tendency in 2 cases (11.1%) out of 18 cases; a transient strengthening and a later weakening in 3 cases (16.6%); a transient weakening then a later strengthening in 11 cases (61.1%); and changes obscure in 2 cases (11.1%). 3. In the tuberculin reaction performed after pulmonectomy with the use of old tuberculin aqueous solution diluted 100-fold, 2, 000-fold, and 10, 000-fold the red color area and the concentration of tuberculin solution show a parallel relationship. 4. In the erythrocyte coagulation reaction performed after pulmonectomy those showing a decreasing tendency in the reaction amounted to 54.5 per cent of the total cases; those showing a weakening and a later strengthening tendency amounted to 18.2 per cent; and in 27-3 per cent no clear-cut fluctuation of the reaction. 5. The tuberculin reaction and erythrocyte coagulation values show a parallel relationship. 6. In the results of paperelectrophoresis it has been found that after pulmonectomy serum albumin is decreased; γ-globulin decreases temporarily but later recovers back to the original level; and α- and β-globulins increase transiently, but each fraction recovers to the level before pulmonectomy after three weeks.