Between September 1, 2011, and February 22, 2012, an unusually high number of hepatitis A cases were reported to the Haute-Normandie Regional Health Agency (ARS HN), with an overrepresentation of cases among the Traveler community in the Rouen metropolitan area (76). A cross-sectional study was conducted to identify risk factors for the spread of the virus among the Traveler population living on sites in the Rouen metropolitan area. In collaboration with the associations Relai d'accueil des gens du voyage (RAGV) and Médecins du monde (MDM), 5 sites were investigated and 34 Traveler families were interviewed (165 people) using two standardized questionnaires (one environmental and one per family). A total of 20 cases of hepatitis A were recorded during the study period, representing an attack rate of 12%. The risk factors identified were: being under 15 years of age, the absence of toilets and showers on the site, the presence of an illegal dump on the site (p < 0.001), and visits to other sites in the metropolitan area (p = 0.012). These risk factors suggest that hygiene recommendations have little impact on the spread of the virus, as their implementation depends on the management of the housing sites. This investigation supported the benefits of a vaccination campaign for the study population while highlighting the importance of promoting this campaign to achieve the highest possible vaccination uptake. (R.A)