To assess whether extended treatment with interferon improves the outcome of hepatitis B e antigen (HBeAg)-negative chronic hepatitis B, 101 consecutive patients were treated with 6 MU of interferon alfa 2b 3 times weekly for 24 months. During the 68-month study, 30 patients (30%) had a sustained response (i.e., normal serum transaminase levels and undetectable hepatitis B virus DNA by non-polymerase chain reaction [PCR] assays), and 15 cleared serum surface antigen. Twenty-five nonresponders, 16 relapsers, and 30 who discontinued treatment were considered treatment failures. Multivariate analysis predicted a sustained response for young age (odds ratio, 0.94; 95% confidence interval, 0.89-0.99; P =.041) and high pretreatment serum levels of immunoglobulin M (IgM) anti-hepatitis B core antigen (HBc) (odds ratio, 4.52; 95% confidence interval, 1.63-12.5; P =.004). Liver disease progressed in none of the sustained responders but in 16 with treatment failure (0% vs. 22%, P =.002); hepatocellular carcinoma (HCC) developed with similar frequency in both groups (7%). Overall, estimated 8-year complication-free survival was longer for the 30 sustained responders than the 71 patients with treatment failure (90% vs. 60%, P <.001), but 8-year patient survival was similar in the 2 groups (100% and 90%). Short complication-free survival was predicted by failure to respond to interferon (hazard ratio, 7.8; 95% confidence interval, 1.8-34.0; P =.006) and high scores for liver fibrosis (hazard ratio, 1.71; 95% confidence interval, 1.17-2.50; P =.005). In conclusion, 24 months of treatment with interferon alfa 2b led to sustained disease suppression in a significant proportion of patients with HBeAg-negative chronic hepatitis B.