The initial filling of the reservoir behind the Petit Saut hydro-electric dam, on the Sinnamary River in French Guiana, threatened the terrestrial and arboreal animals living in the neotropical rainforest being flooded. During a rescue programme between 24 October and 12 November in 1994, many of these animals were checked for infection with trypanosomatids. Overall, 45 blood samples and 54 skin biopsies were collected from 53 mammals (of 13 species representing five orders) and blood samples were also taken from each of nine reptiles (six species from four families). When the skin biopsies and the buffy-coats from the blood samples were cultured in NNN medium, 10 of the cultures, each initiated with mammalian blood, were found to be positive for trypanosomatids. Multilocus enzyme electrophoresis (MLEE) on cellulose acetate plates, with 20 enzyme systems, was then used to investigate each of the positive cultures. The results were analysed by clustering from a genetic distance matrix, using the unweighted pair group method with arithmetic averages (UPGMA), and applying a bootstrap procedure to Wagner parsimony trees. A stock obtained from Didelphis marsupialis was identified as a zymodeme of Trypanosoma cruzi (Miles' zymodeme 1) known to cause Chagas disease in French Guiana. Five stocks (one each from Bradypus tridactylus, Tamandua tetradactyla and Alouatta seniculus and two from Saguinus midas) were of a single zymodeme close to Trypanosoma rangeli reference stock RGB. This is the first confirmation of the presence of Tr. rangeli in French Guiana, and the first time that it has been identified, by iso-enzyme analysis, in the neotropical primates A. seniculus and S. midas. Two other stocks, isolated from Choloepus didactylus, were related to Endotrypanum schaudinni reference stock LEM 2790. Although the remaining stocks, one from C. didactylus and the other from A. seniculus, clustered together on UPGMA and in a Wagner tree, they did not appear to be related to any of the reference stocks included in the UPGMA dendrogram.