Eighty patients with chronic hepatitis C who completed a previously reported randomized controlled trial on the efficacy of interferon-alpha 2b were followed up for at least 36 mo after therapy discontinuation. Seventeen patients (21.2%) maintained normal ALT values throughout the follow-up; 63 (78.8%) either did not normalize the levels of ALT or relapsed during the follow-up. A significantly greater proportion of patients treated with 3 million units of interferon three times a week subcutaneously for 48 wk were long-term responders compared with patients treated for 24 wk. Sex, age, hepatitis C virus antibody status, source of infection and pretreatment levels of ALT were not predictive of long-term response. Cirrhosis was found to be an unfavorable predictive factor. After 3 yr of follow-up, clearance of viremia was observed in 58.9% of the 17 long-term responders but in none of the non-responders (p = 0.002). E2-NS1 antibody tested negative in 88.2% of long-term responders and in 14.3% of nonresponders (p = 0.001). Fifty-nine percent of long-term responders tested negative for C100-NS4 antibody compared with 14.3% of nonresponders (p = 0.031). No significant change was observed in other antibodies. Four long-term responders underwent liver biopsy 2 yr after discontinuation of therapy. All four patients had normal liver histology compared with baseline assessment of chronic active hepatitis in three and chronic persistent hepatitis in the other. Three of the four were negative for serum hepatitis C virus RNA.