Cryptococcosis associated with AIDS is mainly due to Cryptococcus neoformans var. neoformans which is found in saprophytic form in pigeon droppings. This variety has been isolated in Central Africa, particularly in Zaire, Burundi and Rwanda, from dust collected from the houses of patients with cryptococcosis. Several patients confirmed frequent contact with pigeons. Recent studies in Australia demonstrated a link between the yeast and Eucalyptus of the camaldulensis and teriticornis species. These two species were imported to Central Africa from Australia. Examination of 657 Eucalyptus specimens collected in Rwanda did not detect the yeast in any type of tree. This finding casts doubt on the role of Eucalyptus in the ecology of cryptococcosis in Central Africa.