1. Patients receiving regular hemodialysis treatment who are permitted to select their own diets are in danger of a protein deficiency manifested by a significant reduction in serum transferrin and in complement C3c. 2. Correlation analysis within the dialysis group revealed no secure connexion between the complement C3c and total hemolytic activity respectively, and transferrin levels. 3. Analysis of diets showed that protein intake and the serum transferrin level correlate. No such correlation was found for the complement C3c or total hemolytic activity. 4. Low transferrin levels in the serum appear to result in more severe anemia among dialysis patients. 5. Knowledge of the serum transferrin level permits much more exact assessment of the protein metabolism in regular hemodialysis patients than knowledge of the total hemolytic activity or the level of the complement C3c.