A follow-up study was made of 94 chronic hepatitis C patients at a hepatitis clinic in Brazil, after interferon alpha (IFN-alpha) therapy, to determine the influence of anti-interferon antibodies on treatment outcome. Patients diagnosed as having chronic hepatitis C, confirmed by PCR (HCV RNA) and liver biopsy, were treated with interferon alpha 2a or 2b for at least six months, and were followed up for 24 week...