When a so-called free diet is granted there is the danger of a protein deficit, which can be proved in a significant decrease of the serum transferrin and of the complement factor E3c, in patients in the chronic haemodialysis programme. 2. Within the group undergoing dialysis a correlation analysis did not result in a statistically ascertained connection between the complement factor C3c and the total haemolytic activity and the transferrin, respectively. 3. On the basis of a diet analysis a connection between the protein supply and the serum transferrin level could be established, which was not to be proved for the complement factor C3c and the total haemolytic activity, respectively. 4. Low transferrin values in the serum seem to be followed by a deterioration of the anaemia situation of the patient undergoing haemodialysis. 5. Compared with the total haemolytic activity and the complement factor C3c the determination of the serum transferrin allows an essentially exacter information about the protein metabolism of the patient undergoing a chronic haemodialysis.