Summary. The natural history of chronic hepatitis C presenting with no/minimal liver fibrosis is uncertain with controversies on risk of progression and need for antiviral treatment. We studied rates and determinants of fibrosis progression in initially mild chronic hepatitis C. One hundred and six patients (mean age 41.65 ± 12.83 years) with chronic hepatitis C virus infection and no/minimal fibrosis in the initial liver biopsy (F0/F1 by METAVIR score) were followed prospectively while untreated with repeated biopsy after 5 or more years (mean interval 7.8 ± 1.51 years). Patients showing fibrosis progression were compared with nonprogressors for baseline and follow-up parameters. Sixty-four patients (60.4%) showed fibrosis progression including 13 of 27 (49%) with F0 and 51 of 79 (65%) with F1. Progression to F3 or cirrhosis was seen in 36% of those with F1 initially. Fibrosis progression (ΔF/year) was associated with age (P < 0.0001), baseline and follow-up alanine aminotransferase (ALT) (P = 0.005), histological activity (P = 0.004) and steatosis (P = 0.002) in the initial biopsy and use of alcohol (P = 0.008). Thus liver fibrosis progression occurs in two-thirds of patients with initially mild chronic hepatitis C within 5–10 years and advanced fibrosis/cirrhosis develops in one-third of those with F1 initially. Fibrosis is facilitated by older age and alcohol and associated with inflammatory activity and ALT levels. Antiviral therapy should be considered in mild chronic hepatitis C.