Few studies have analysed the evolution of HCV markers in chronic hepatitis C (CHC)-treated patients. We have evaluated the presence or absence of serum and liver HCV-RNA, the core antigen (HCV-cAg) and the loss of specific antibodies (anti-HCV), in long-term sustained responders (SR). One hundred and seventy-six patients (132 SR and 44 nonresponders (NR) were included in the study. HCV-RNA was determined in serum and liver by a commercial PCR-kit. HCV-Ag was determined by ELISA and specific antibodies against HCV by means of a commercial line immunoblot assay (LIA) technique. Serum HCVcAg was found positive in three (4.2%) SR and in one (4%) NR (NS). Four SR (3.6%) and 44 NR (100%) were also HCV-RNA (+) in liver tissue. Two patients were HCV-cAg (+). A good correlation was found between the serum levels of HCV-cAg and HCV-RNA (r = 0.847, P < 0.001). Specific antibodies (anti-HCV) were determined by LIA in 45 patients. A decrease was found in the number of patients who presented reactivity to bands E2 and NS4 when we compared SR with a follow-up of more than 5 years with NR and SR with a follow-up <5 years (P < 0.01 and 0.005). A good correlation was found between the HCV-cAg and HCV-RNA serum levels in CHC-treated patients (P < 0.001). Few SR (3.6%) had HCV-RNA in the liver, and HCV-cAg (1.8%) in serum. In SR with more than 5 years of follow-up a clear tendency exists in the trend to clarify the bands E2 and NS4 of anti-HCV in serum.