Understanding viral dynamics during acute hepatitis C virus (HCV) infection can provide important insights into immunopathogenesis and guide early treatment. The aim of this study was to investigate the dynamics of HCV RNA and alanine transaminase (ALT) levels during recent HCV infection in the Australian Trial in Acute Hepatitis C (ATAHC). ATAHC was a prospective study of the natural history of recently acquired HCV infection. Longitudinal HCV RNA and ALT levels were compared among individuals with persistent infection and spontaneous clearance. Among those with HCV persistence (n = 104) and HCV clearance (n = 30), median HCV RNA (5.2 vs. 4.1 log IU/ml, respectively) and ALT levels (779 vs. 1,765 IU/L, respectively) were high during month two following infection, and then declined during months three and four in both groups. Among those with HCV persistence, median HCV RNA was 2.9 log IU/ml during months four, increased to 5.5 log IU/ml during month five, and remained subsequently relatively stable. Among those with HCV clearance, median HCV RNA was undetectable by month five. Median HCV RNA levels were comparable between individuals with HCV persistence and HCV clearance during month three following infection (3.2 vs. 3.5 log IU/ml, respectively; P = 0.935), but markedly different during month five (5.5 vs. 1.0 log IU/ml, respectively; P < 0.001). In conclusion, dynamics of HCV RNA levels in those with HCV clearance and HCV persistence diverged between months three and five following infection, with the latter time-point being potentially useful for commencing early treatment. J. Med. Virol. 86: 1722–1729, 2014. © 2014 Wiley Periodicals, Inc.