Weight for age, weight for height, the concentration of albumin, prealbumin, and transferrin together with the proteinase inhibitors α₁-antitrypsin, α₁-antichymotrypsin, α₂-macroglobulin, and the acute-phase reactants α₁-acid glycoprotein and haptoglobin were determined in six marasmus and seven kwashiorkor children; marasmus-kwashiorkor children were admitted with diarrhea. The results were compared with those from six healthy preschool children. Serum protein concentration from the children suffering from protein-energy malnutrition were measured at the 2nd, 8th, 29th, and 50th day after hospital admission. The anthropometric measurements, prealbumin, albumin, and transferrin were lower in the protein-energy malnutrition children compared with the healthy preschool children. Prealbumin and albumin indicated a lower nutritional status in the kwashiorkor, marasmus-kwashiorkor group compared with the marasmus group. α₂-Macroglobulin and α₁-antitrypsin were lower in the protein-energy malnutrition groups compared with the healthy preschool children. Both serum proteins were significantly lower at the 2nd day compared with the 50th day in the kwashiorkor, marasmus-kwashiorkor group, whereas α₁-antitrypsin values remained almost the same level in the marasmus group from the 2nd day up to the 50th day. α₁-Acid glycoprotein and α₁-antichymotrypsin were higher in the marasmus group at the 2nd day compared with the healthy preschool children. α₁-Acid glycoprotein at the 2nd day of the kwashiorkor, marasmus-kwashiorkor group were higher compared with the 50th day of that group. α₁-Antichymotrypsin levels at the 2nd day of the marasmus group were higher compared with the 2nd day of the kwashiorkor, marasmus-kwashiorkor group. Haptoglobin did not differ between the groups. Variations of α₂-macroglobulin, α₁-antitrypsin, and albumin during treatment for one marasmus and one kwashiorkor case complicated by frequent periods of fever were compared with one marasmus and one kwashiorkor case with straight recovery. The results are discussed in respect of the possible role of α₁-antitrypsin and α₂-macroglobulin in the influence of these inhibitors on the balance of catabolism and anabolism of protein in protein-energy malnutrition complicated by infection, where the proteinase inhibitors might also inhibit the mobilization of body's own protein.