The etiology and pathophysiology of schizophrenia remain unknown. It has been postulated that infectious-autoimmune process may play a role in the pathogenesis of symptoms in some schizophrenic patients. Findings of altered interleukin(IL) regulation have been regarded as additional proof that schzophrenia has an infectious-autoimmune background. In the present study, we measured mitogen-stimulated production of and serum level of IL-$1{eta}$, IL-2, IL-6 using ELISA in 16 neuroleptic-free schizophrenic patients and in 16 age, sex matched healthy controls. The results were as follows : 1) There was a significant decrease of IL-2 production in schizophrenic patients than in normal controls(respectively $1.90{pm}0.13ng/m{ell}$, $2.79{pm}0.14ng/m{ell}$, p<0.001). But there was no significant difference of IL-$1{eta}$ production and IL-6 production between schizophrenic patients and normal controls. 2) There was a significant increase of serum level of IL-2 in schizophrenic pateitns than in normal controls(respectively $184.8{pm}12.8pg/m{ell}$, $104.2{pm}34.2pg/m{ell}$, p<0.01). Serum level of IL-$1{eta}$ was partially detected in both groups and serum level of IL-6 was not detected in both groups. 3) There was no significant differences of IL-$1{eta}$, -2, -6 production & serum level of IL-2 according to male vs female, paranoid type vs undifferentiated type, drug-naive group vs drug-free group in schizophrenic patients. 4) There was significant correlation between IL-$1{eta}$ and IL-6 production(r=0.86, p<0.001). No correlation between IL-$1{eta}$, -2, -6 production, serum level of IL-2 and age, duration of illness, and BPRS score was found. It has been suggested that the low lymphocyte production of IL-2 in the patients with autoimmune disease occurs because the T cells are activated and lymphocyte-derived IL-2 has been released into the serum. The authors suggest that decreased IL-2 production in our schizophrenic patients is due to increased IL-2 serum level in those patients. Thus our finding of low IL-2 production and high serum level of IL-2 in our schizophrenic patients is compatible with the possibility that our patients have an autoimmune process. Further study on relationship between IL alteration and other immunological abnormalities(the presence of serum autoantibody and of anti-brain antibody, $CD4^+$, $CD8^+$ cell index, etc) in schizophrenic patients will be warranted.