During the period between January 1975 and August 1976, 203 liver biopsies were received at the Singapore General Hospital from patients with a variety of liver diseases. A histological diagnosis of chronic hepatitis was made in 29 patients: 13 cases of Chronic Aggressive Hepatitis (C.A.H.). 10 cases Chronic Persistent Hepatitis (C.P.H.) and 6 of Chronic Lobular Hepatitis (C.L.H.). C.P.H. and C.L.H. were found mainly in the third and fourth decades. C.A.H. was more common in the fifth to seventh decades and occurred principally in females. Hepatitis B antigenaemia was detected in 48.3% of these cases using the immunoelectroosmophoresis (EOP) technique and showed an even scatter in all histological sub-types. Using the reverse passive haemagglutination (rPHA) method for detection by HBs antigen and the radioelectrocomplexing (REC) method for anti-HBs, an immune sub-group (HBs Ag+/anti-HBs+) was identified in greater proportions in C.A.H. and C.P.H. compared to normal controls. This was interpreted to mean that these patients suffered from a primary immunodeficiency characterized by failure of production of high avidity anti-HBs with resulting failure to clear HBsAg leading to perpetuation of liver damage due to circulating immune complexes. It is also suggested that patients with C.P.H. belonging to this immune sub-group may progress to C.A.H. with its more ominous prognosis.