This paper reports the results of parasitological studies of stools carried among the amerindian population of the Guaporé and Mamoré river valleys, in the State of Rondônia, Brazil The population is constituted mainly of Pacaas-Novos indians and other smaller groups (Massacá, Ajuru, Canoé, Jabuti, Mequém, Tupari and Macurap). The following species were found: Ascaris lumbricoides (21,3%), Trichuris trichiura (1,6%)Ancilostomidae (12,2%), Strongyloides stercoralis (3,9%), Enterobius vermicularis (2,0%), Hymenolepis nana (0,3%), Capillaria sp. (0,2%), Giardia lamblia (12,7%) and Entamoeba hystolitica (8,8%). The results are discussed and compared with those obtained by other authors among different Amazonian groups.
