A high frequency (25%) of anti-hepatitis C virus (HCV) antibodies is observed in French hemodialyzed patients; this is associated with detectable viremia in 85% and results in chronic hepatitis in more than 90%. We conducted a pilot study to examine the tolerance and efficacy of alpha-2b Interferon therapy upon HCV infection in hemodialyzed patients. Nineteen anti-HCV positive hemodialyzed patients were given a standard alpha-2b interferon regimen (3 megaunits subcutaneously three times weekly, following each hemodialysis) over six months as a treatment of biopsy-proven chronic hepatitis (N = 16) or acute hepatitis (N = 3). Thirteen of these 19 had increased levels of aminotransferase at the time of treatment. Serum HCV RNA was tested qualitatively and quantitatively by the polymerase chain reaction and the bDNA test, respectively, at the beginning and at the end of antiviral treatment, and a third time at least six months after the end of therapy (mean follow-up 18 +/- 9 months). HCV genotype was determined in the 15 patients who had detectable HCV RNA before treatment. The biological response (long-term response, relapse or non-response) was defined as usual according to the serum aminotransferase levels during therapy and at least six months after. A post-treatment liver biopsy, allowing comparison with semiquantitative pathological scores, was performed in 14 patients. Only one of the 19 treated patients did not complete therapy because of poor tolerance, while 18 of the 19 fairly tolerated a complete six month course of alpha-2b interferon.(ABSTRACT TRUNCATED AT 250 WORDS)