Five of 72 patients dialysed at the same dialysis unit developed elevated alanine aminotranspherase (ALT) levels attributed to acute non-A, non-B hepatitis (NANBH). Histopathologic findings consistent with NANBH were present in four of them. Serological screening for antibodies to hepatitis C virus (anti-HCV) was performed in all 72 cases. Three of the patients with NANBH and 2 of the other 67 patients had positive tests. Low and transient levels of anti-HCV were noted in 2 patients with NANBH in spite of chronic hepatitis. Only 1 of 5 patients with NANBH was known to have had blood transfusions indicating other, as yet undefined, modes of transmission of HCV for the others. Although antibody responses to HCV might be transient or low, testing for anti-HCV should be considered in dialysis populations.