The immunological system of patients with anorexia nervosa seems to react in a non typical and, up to now, obscure way. We do not observe greater ability to catch infectious diseases while damage due to other reasons leads as a rule to breakdown of resistance mechanisms thus giving increased receptivity to infections. The works concerning the immunological functions in anorexia nervosa are not heterogeneous and concern small groups of patients. The research was made upon 29 female patients aged 12 to 20 with the diagnosis of anorexia nervosa due to DSM-IV criteria. The research was made before starting the treatment and 6 weeks after the withdrawal of all anorexia nervosa symptoms. The research results showed that in the female patients there were no essential disturbances in the scope of electrophoresis of serum protein. Testing the protein of acute phase CRP as well as the estimation of their main microheterogeneity did not show significant deviation from the norm, which shows any features of early and later activation of the immunological system. However, a slight decrease of CD3 and low coefficient CD 4/8 during the disease were observed. After the symptoms retreated the coefficient became normal. Summing up we can state that the immunological system in patients with anorexia nervosa, in spite of great cachexia, did not show significant changes. The stated specific dysfunctions may be connected with a subtype of disease and other neurotransmitter mechanisms, which still requires to be confirmed in further research.