Following the occurrence of a fatal case of hepatitis A in a 12-year-old child, the DSDS of French Guiana conducted an epidemiological and environmental investigation to identify a potential outbreak, detect situations posing a risk of secondary transmission, and propose recommendations for the prevention of HAV infections tailored to the context of French Guiana. A search for other cases of hepatitis A was conducted at private and hospital laboratories on the island of Cayenne. Environmental investigations were carried out at the case’s residence and in the two villages where cases linked to the reported case reside. In total, 19 cases testing positive for anti-HAV IgM were identified between January 1 and May 31, 2004. Six of the 19 cases belong to the same community whose lifestyle presents risks of HAV infection equivalent to those in developing countries (community traditions, lack of a drinking water and sanitation system). Among the other documented cases, 4 children from villages in the Maroni region present equivalent risks of infection. The other 9 identified cases appear to be isolated and primarily involve adults scattered across several municipalities in the department. These results corroborate the contrasting patterns of exposure to enteric diseases in French Guiana. Recommendations are made, in the immediate term, regarding the benefits of vaccinating individuals who habitually reside in a low-endemic area (urban areas of French Guiana, the Antilles, metropolitan France, etc.) who travel to high-risk areas; and, in the longer term, on the need to improve access to safe drinking water and sanitation for a portion of the French Guiana population as part of a public health program integrating environmental and health-related approaches. Finally, it is also proposed to identify the hepatitis A vaccination strategies best suited to the epidemiology of the disease in French Guiana and to assess the feasibility of implementing them. (R.A.)