Background: A recent hepatitis C virus (HCV) outbreak has been suspected of being caused by an infusion of intravenous immune globulin. Study Design and Methods: Three laboratories were mandated by the French regulatory agency to prospectively screen on a national scale those persons having received suspected batches: 233 exposed patients were recalled and tested for HCV antibody and for HCV RNA. Results: Nineteen patients (8.1%) were found positive for HCV RNA; 7 of these 19 were positive for the HCV antibody, Conclusion: The link between HCV infection and intravenous immune globulin was reinforced by the overrepresentation of the 2b genotype (58%), which contrasts with the low prevalence of this genotype in France (1%).