The long-term usefulness of interferon-alpha (IFN-alpha) in chronic hepatitis B remains controversial. To investigate the long-term efficacy of IFN-alpha therapy in chronic hepatitis B, 62 Japanese patients, including 27 patients treated with IFN-alpha (IFN group) and 35 patients without antiviral therapy matched by age and sex as controls (control group), were followed up for 2-14 years. At entry, the serum alanine aminotransferase (ALT) level in the IFN group was significantly higher than that in the control group (238.6+/-250.1 vs. 142.3+/-152.1 IU/l, P < 0.05). The prevalence of genotype C was 89%, with no difference between the two groups (93 vs. 86%). There was no significant difference in the presence of the precore mutation or the dual core promoter mutations between the IFN and control groups (37 vs. 46%, 74 vs. 66%). After long-term follow-up, the rate of sustained HBeAg seroconversion was comparable in the two groups (33 vs. 31%). Normalization of serum ALT level was seen in 44% of the IFN group and 51% of the control group, with no difference. There was also no difference in the percentage of cases with loss of serum HBV-DNA by PCR assay between the two groups (33 vs. 29%). During follow-up, two patients of the control group and three patients of the IFN group developed cirrhosis, and one of the IFN- treated patients progressed to hepatocellular carcinoma. The results of this long-term follow-up study showed that no benefit of IFN-alpha treatment was detectable during long-term follow-up in Japanese patients with chronic hepatitis B.