One hundred and twenty HBsAg positive patients with chronic liver disease, 94 with CAH and 26 with CPH, were studied in order to characterize chronic HBsAg positive hepatitis virologically. All patients came from a geographical area (Campania, Italy) with a high prevalence of HBV and HDV infection. Each patient was tested for the presence of HBsAg, HBeAg, anti-HBe and anti-delta in serum (by RIA techniques), and of HDV (by direct immunofluorescence) and HBcAg (by indirect immunofluorescence and PAP-immunoperoxidase) in liver biopsy specimens. Anti-delta serum positivity was remarkably more frequent in patients with CAH (40%) than in those with CPH (19%). Delta-Ag was found in 94.7% of the anti-delta positive patients with CAH, but in none of the five anti-delta positive patients with CPH. In contrast, the frequency of HBcAg tissue positivity was similar in CAH and CPH. Positivity for HBcAg was less frequent in CAH with cirrhosis than in CAH without cirrhosis, while there was no difference in the prevalence of delta-Ag.