The aetiopathogenesis of non-cirrhotic portal fibrosis (NCPF), a common cause of portal hypertension in India, is not known. To study the immune status of NCPF patients and to see whether immunological mechanisms have a role to play, humoral and cell-mediated immunological studies were carried out in 43 patients with NCPF and compared with equal number of matched healthy controls and 31 patients with compensated liver cirrhosis. Serum immunoglobulin A (IgA) and complement (C3, C4) levels were significantly (P less than 0.001) lower in NCPF patients compared with controls and cirrhotics. There was no significant difference between the total or the relative concentration of the immunoglobulins and complements between NCPF patients and healthy controls, but, in patients with cirrhosis, concentration of all the immunoglobulins was higher. The cutaneous response to dinitrochlorobenzene was poorer in patients with NCPF, but the difference between cirrhotics and controls was not significant. A decrease in the suppressor/cytotoxic (T8) phenotype of lymphocytes in the peripheral blood and an increase in the ratio of helper/inducer (T4) and T8 lymphocytes was seen in patients with NCPF and cirrhosis. Although these results indicate definite immunological abnormalities in NCPF patients, their role in the pathogenesis of NCPF remains to be investigated.