Extracorporeal photopheresis (ECP) is approved for treatment of cutaneous, T-cell lymphoma. Evidence suggests that ECP can induce an immune response against tumor antigens expressed by malignant T lymphocytes. We theorized that if HCV-infected PBMCs express viral antigens, ECP could demonstrate antiviral activity by eliciting an immune response against these antigens. Fifteen cirrhotic patients with genotype-1 HCV, who had previously relapsed or not responded to interferon-alpha (IFN-alpha) therapy were stratified by their HCV RNA titer into one of three treatment groups: (1) ECP alone, (2) ECP + 3 MIU IFN-alpha2a subcutaneously three times a week and (3) ECP + 6 MIU IFN-alpha2a subcutaneously three times a week. All patients received treatment for 24 weeks. Group 1 had no significant decrease in HCV RNA. Two patients in group 2 had undetectable HCV RNA at the end of treatment. One patient in group 3 had undetectable HCV RNA at the end of treatment. However, HCV RNA was detected in all three patients during follow-up. ECP alone or with IFN-alpha was well tolerated. ECP alone demonstrated no clear antiviral activity. The combination of ECP and IFN-alpha resulted in an end-of-treatment response (ETR) in three of 10 patients. All responders had elimination of serum HCV RNA by three months, although no patient had a sustained response. More intensive therapy for a longer duration may result in sustained responses. A multicenter trial is now underway.