To determine the effect of interferon-alpha2b (IFN-alpha2b) on the long-term suppression of hepatitis C virus (HCV) RNA in patients with persistently normal or near normal alanine aminotransferase (ALT) activity, 76 previously untreated patients with serum HCV RNA and ALT levels <1.5 times the upper limit of normal (ULN) were randomized to receive either interferon-alpha2b (IFN-alpha2b) 5 MU three times a week for 24 weeks (n = 37) or no treatment (n = 39). HCV RNA testing was performed at the end of treatment and after a 6-month follow-up period. Intention-to-treat analysis showed that HCV RNA was detected significantly less frequently in treated than in untreated patients, at the end of both treatment and follow-up (43.2% vs. 7.7%, p < 0.001, and 21.6% vs. 5.1%, p = 0.033, respectively). Among treated patients, sustained virologic response was significantly higher in non-1 than in genotype 1 patients (8 of 26 or 30.8% vs. 0 of 11, p = 0.038). According to multiple logistic regression, untreated patients had a 13.5 times greater risk to be HCV RNA-positive compared with treated patients (p = 0.040). ALT levels flared up in 3 treated and 9 untreated patients (p = 0.07), suggesting that these flare-ups are related to the natural course of chronic HCV infection rather than to IFN-alpha2b. Thus, such patients could benefit from an IFN-alpha2b in combination with ribavirin regimen.