Cirrhosis is a frequent and severe event in the course of chronic hepatitis C, but it is unclear why some patients develop cirrhosis after a given period whereas others do not. We studied a large cohort of patients with chronic hepatitis C to determine the role of the route of transmission of hepatitis C virus (HCV) in the onset of cirrhosis. Six thousand six hundred sixty-four patients were enrolled in a nationwide survey of chronic hepatitis C in France. We first randomly defined a representative sample of 30 hospitals with medical units managing patients with HCV infection. All patients with chronic hepatitis C were enrolled if hepatitis C was diagnosed or treated in these units in 1991, 1992, or 1993. A questionnaire was filled in from the patients' charts and covered demographic data, risk factors for HCV infection, clinical and histological data, hepatitis B virus (HBV) and human immunodeficiency virus status, and alcohol intake. Descriptive statistics were prepared, and factors potentially related to the onset of cirrhosis were identified by means of univariate analysis followed by stepwise logistic regression analysis. Among the patients enrolled, 21.4% had biopsy-proven cirrhosis. Prevalence of cirrhosis markedly varied according to the route of transmission of HCV. It was significantly more frequent in blood recipients (23.4%) than in drug users (7.0%). Although the occurrence of cirrhosis was dependent on disease duration, it remained more frequent in blood recipients than in drug users for a given duration. Apart from the route of transmission, excessive alcohol intake was also associated with a higher risk of cirrhosis (34.9% vs. 18.2%; P < .001), and so was HBV infection (24.6% vs. 21.1%; P < .05). These factors acted independently of the route of transmission. Hepatocellular carcinoma was observed in 3.6% of all patients and in 17.8% of cirrhotic patients, and its occurrence was strongly and mainly related to the presence of cirrhosis. In conclusion, cirrhosis occurred in about 20% of the HCV-infected patients in this study and was more frequent in blood recipients than in drug users, independently of disease duration. Expected changes in the epidemiology of HCV infection might modify the risk of developing cirrhosis and, thereafter, cancer.