The relationship between hepatitis C virus RNA and hepatitis C virus‐associated antibodies (antibody against the putative capsid protein and C‐100 antibody) was determined by nested polymerase chain reaction and enzyme‐linked immunosorbent assay in serial serum samples obtained from eight chimpanzees experimentally infected with hepatitis C virus. Three different patterns emerged from the polymerase chain reaction data: the first (group 1) was acute resolving hepatitis with transient appearance of HCV RNA (two cases). The second (group 2) had chronic hepatitis with persistent hepatitis C virus RNA positivity (four cases) and the third (group 3) had chronic hepatitis with intermittent appearance of hepatitis C virus RNA (two cases). In four of eight animals, hepatitis C virus RNA was first detectable in serum 1 wk after inoculation. Although serum HCV RNA was detected in all infected chimpanzees, two were positive only for antibody against the putative capsid protein, whereas two were positive only for antibody to C‐100 antigen. In four of eight cases, antibody against the putative capsid protein appeared earlier than did antibody to C‐100 antigen, was detected just before or coincident with rising glutamate pyruvate transaminase values and remained positive for a long time even after recovery. Six of eight animals (75%) were still hepatitis C virus RNA positive 1 yr after inoculation, suggesting that the risk of development of the chronic carrier state is high in hepatitis C virus infection. Furthermore, there did not appear to be a good correlation between antibody titer in serum and hepatitis C virus infectivity titer. (Hepatology 1992;690–695).