Four hundred and four patients (273 men, 131 women) aged 3 to 85 years with chronic Hepatitis B virus (HBV) infection seen during a five year period were analysed. At presentation, 177 patients (44%) were Hepatitis B e Antigen (HBeAg) positive (mean age 32 years) and 217 patients (54%) were anti-HBe-positive (mean age 40 years). Ten patients (2%) were negative for HBeAg and anti-HBe. Serum HBV-DNA was detected in 169 patients (42%). 85% of the HBeAg-positive patients had detectable serum HBV-DNA and 9% of the HBeAg-negative patients were positive for serum HBV-DNA. The mean serum Alanine amino-transferase (ALT) and Aspartate amino-transferase (AST) levels were higher in HBeAg-positive patients (75 and 52 iu/l) than in HBeAg negative patients (46 and 37 iu/l) (P less than 0.001). Liver biopsies were performed in 135 patients. Fifty-three (39%) had minimal changes, 61 (45%) chronic hepatitis (CPH, CLH & CAH) and 21 (16%) cirrhosis. There was no significant difference in the histologic distribution between HBeAg-positive and HBeAg-negative groups. Two hundred and fifty eight patients were followed up for a mean duration of 2 years (range 3 to 108 months). The cumulative probability of clearing HBeAg at the end of the first, second and third year were 14%, 16% and 18% respectively. Of these, the cumulative probability of developing anti-HBe over one, two and three years were 8%, 9% and 11% respectively. Reversion to HBeAg occurred in 1.5% of patients who were HBeAg-negative at presentation and 11% of HBeAg-positive patients who cleared HBeAg.(ABSTRACT TRUNCATED AT 250 WORDS)