Key points: - 26 of the 30 voluntary reference centers established in 1995 participate in a surveillance network tracking changes in the epidemiological and clinical characteristics of patients with hepatitis C at the time of initial diagnosis; - The proportion of incidentally detected HCV-positive serology increased from 34% in 2000 to 50% in 2003; - The proportion of patients infected through transfusion prior to 1991 decreased from 35% to 29%; - slight decrease in the proportion of severe cases (cirrhosis, hepatocellular carcinoma) at the time of initial diagnosis between 2001 (11.6%) and 2003 (10.1%). (R.A.)