The AA have carried out an epidemiological investigation on the incidence of intestinal parasitosis in groups of populations belonging to the pygmoid tribes Batwa and Hutu living in the Northern and Southern regions of Rwanda (East Africa). Positivity for intestinal parasites (protozoa and/or helminths) reached 100% in the 309 subjects examined, no significant difference in prevalence being observed between the Northern and Southern groups. Among the protozoa, E. coli and E. histolytica were most commonly found, while trichocephalosis and ascaridiasis were the most frequently encountered helminthiasis. The occasional finding of Strongyloides fülleborni infestation should also be pointed out.