To evaluate the efficacy of recombinant interferon (IFN) alpha 2b in the treatment of Chinese patients with chronic hepatitis C, a randomized controlled trial was conducted in 50 chronic hepatitis C patients: 25 patients received 3 million units of subcutaneously injected recombinant IFN-alpha 2b three times per week for 6 months, and 25 patients received no specific treatment were used as controls. At the end of the IFN treatment, 19 patients (76%) in the IFN-treated group normalized serum ALT compared with only 6 patients (24%) in the control group (p < 0.01). Relapse within 6 months after the completion of treatment occurred in 13 IFN-treated patients (68%). Normalized serum ALT was seen in 6 patients (24%) in the IFN-treated group and 1 patient (4%) in the control group 6 months after discontinuation of IFN therapy (p = 0.10). The presence of serum hepatitis C virus (HCV) RNA measured by reverse transcription-polymerase chain reaction was detected at the end of the IFN treatment in all 13 patients who relapsed after cessation of therapy. In only 3 of 25 IFN-treated patients (12%) was the presence of serum HCV RNA not detectable at the end of the IFN treatment or 6 months after cessation of therapy. No patient in the control group had undetectable serum HCV RNA during the study period. Using multivariate logistic regression analysis, the low pretreatment levels of HCV RNA, measured by a quantitative branched DNA amplification assay, was the only independent predictor of a sustained response to IFN therapy (p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)