Over a 5 month period (October 1996 to February 1997), a rotating company of 146 servicemen belonging to the Navy Airborne 6th Regiment were assigned along the Maroni River in French Guyana. During this mission, the medical personnel treated 387 local residents. Etiologies comprised 51 malaria attacks including 46 involving Plasmodium falciparum and 4 rattlesnake envenomations. The most common cause of consultation by military personnel was mycotic and staphylococcal skin infections, but 5 cases involving poor acclimatization were treated during the hot and dry season. Seven malaria attacks involving Plasmodium falciparum including 2 that were severe occurred despite prophylaxis using chloroquine-proguanil. Treatment with halofantrine was successful in all but one case which required combined chemotherapy using quinine and doxycycline. Five cases of cutaneous leishmaniasis were observed in subjects involved in jungle training. No case of HIV infection was detected upon returning home since most personnel either followed the recommendation to abstain from sex (51 p. 100) or used a condom (90 p. 100 of personnel who had sexual relations). These data illustrate the health risks for mainland French nationals in the region of the Maroni River and underline the need for preventive measures and education.