To investigate whether data obtained at the time of diagnosis may serve to predict early seroconversion to anti-HBe in chronic hepatitis B virus infection, we have compared the clinical, pathological and virological features of two groups of patients with untreated HBeAg-positive chronic hepatitis B who showed a markedly different outcome. One group (early seroconverters) included 20 patients who developed a typical seroconversion to anti-HBe within the first year of prospective follow-up. The other group (non-seroconverters) was formed by 21 patients who remained seropositive for HBeAg and still had raised aminotransferase serum levels after at least 2 years of follow-up. The serum aminotransferases, the degree of periportal and lobular lesions, the amount of liver fibrosis and the total score index of histological activity were significantly higher but the amount of HBcAg in liver was smaller in early seroconverters. Stepwise logistic regression analysis demonstrated that the alanine aminotransferase serum levels, the Knodell's index of histological activity and the amount of HBcAg in liver had significant value as independent predictors of early seroconversion. Calculation of the probability of seroconversion for individual cases showed marked differences between the two groups of patients, suggesting that early seroconversion to anti-HBe may be predicted in some patients with chronic hepatitis B.