The prevalence of the anti-HBc antibodies was studied in 54 patients with chronic liver disease and in a group of controls pair-matches. The meaning of the anti-HBc antibodies titer in the patients HBsAg negative is discussed. From our data, obtained by Radioimmunoassay, anti-HBc titers I:I000 seem to indicate an ongoing or recent viral replication, being probative, even in the absence of the HBsAg marker, for the viral etiology.