The natural course of non-A, non-B (type C) hepatitis was studied in 62 haemodialysis patients. From the onset of the disease, serum alanine aminotransferase levels were monitored monthly for 9-218 mon (median 115). After fluctuation of aminotransferase levels for 1-206 mon (median 39), 57 (92%) patients showed normalization of these levels lasting until the end of the follow-up, which was for > 2 yr in 31 (50%) cases and for > 5 yr in 15 (24%) cases. At the end of follow-up, hepatitis C viraemia was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and branched DNA (bDNA) assay. Viraemic levels were significantly lower in the 15 patients with normal aminotransferase for > 5 yr (median RT-PCR + ve/bDNA-ve, range RT-PCR-ve to 10(6.7) Eq/mL) than in the 47 cases with normal levels for < 5 yr (median 10(6.6), range RT-PCR + ve/bDNA-ve to 10(7.6) Eq/mL) (P < 0.01). Moreover, a significant inverse relation was observed between viraemic levels and the duration of aminotransferase normalization (r = -0.46, P < 0.01). These findings indicate that biochemical remission of hepatitis C may be frequent in haemodialysis patients and may be related to viral attenuation.