Introduction - As part of the first national program to combat hepatitis C (1999), the InVS established a hepatitis C surveillance system through reference centers. This article describes the epidemiological and clinical characteristics of patients newly diagnosed with hepatitis C who were enrolled in 2001 and 2004. Methods - Twenty-six reference centers (hepatology departments) voluntarily participate in the surveillance system. A case is defined as a patient with positive anti-HCV antibodies seen for the first time at the participating center. Clinical and epidemiological data are routinely collected, including the circumstances of seropositivity detection, risk exposures, HCV RNA status (PCR), viral co-infections, excessive alcohol consumption, and disease severity. Results - The number of cases included was 3,906 in 2001 and 3,417 patients in 2004, including 1,509 women (median age 48 years) and 1,908 men (median age 42 years). The proportion of HCV seropositivity detected during routine screenings rose from 41% in 2001 to 51% in 2004. The two most common modes of transmission were transfusion prior to 1991 among women and intravenous drug use among men, accounting for 36% and 46% of cases, respectively, in 2004. The proportion of viremic patients (HCV RNA positive) remains stable (90%). Excessive alcohol consumption was found in 51% of male drug users in 2004. The proportion of cirrhosis remains stable at approximately 10%. Conclusion - This system allows for the monitoring of indicators such as the method of detection, risk factors, and the severity of hepatitis C at the time of diagnosis. The results reinforce the need to address excessive alcohol consumption. (R.A.)