Summary. The possible effect of interferon-alpha (IFNa) on liver fibrosis progression has not been adequately studied in chronic hepatitis B. We evaluated 147 patients with HBeAg-negative chronic hepatitis B who had ≥2 liver biopsies and had been treated with IFNa (n = 120) or had remained untreated (n = 27). The median interval between the two biopsies was 24 (12–160) months. All biopsies were scored blindly by a single liver histopathologist according to the classification of Ishak et al. (J Hepatol 1995; 22: 696–699). IFNa induced sustained biochemical response in 30, initial response and subsequent relapse in 57 and no response in 33 patients. Fibrosis improved in 17.5% of treated (sustained responders: 40%, relapsers: 9%, nonresponders: 12%) and 4% of untreated patients and worsened in 34% (sustained responders: 7%, relapsers: 40%, nonresponders: 48%) and 70% of cases, respectively (P = 0.002). The annual rate of fibrosis progression was worse in the untreated (0.427 ± 0.119) than in treated patients (0.067 ± 0.052, P = 0.001). However, the fibrosis progression rate in the untreated patients was not significantly different than the net fibrosis progression rate (after subtraction of IFNa duration) in nonresponders or relapsers. In multivariate analysis, worse fibrosis progression rate was associated with older age (P = 0.010), worse baseline grading score (P < 0.001), lower baseline fibrosis (P = 0.035) and the type of response to IFNa (P = 0.032). In conclusion, in HBeAg-negative chronic hepatitis B, IFNa significantly reduces the rate of fibrosis progression, but such an effect is mainly observed in patients with sustained biochemical responses. In relapsers and nonresponders, fibrosis benefit equals the treatment period. The strongest factor associated with fibrosis progression is the change in necroinflammatory activity.