One hundred and fifty-four human dwellings in the metropolitan area of Rio de Janeiro, Brazil were studied. A total of 824 samples of indoor dust, outdoor soil and avian droppings were collected. Cryptococcus neoformans var. neoformans was isolated from 20 (13%) dwellings, comprising five (15.6%) of 32 dwellings of patients with AIDS-associated cryptococcosis; four (8.9%) of 45 dwellings of patients with AIDS but without cryptococcosis; and 11 (14.3%) of 77 dwellings of apparently healthy individuals (P>0.05). The principal factor associated with domiciliar contamination by C. neoformans var. neoformans was the presence of avians in the domestic environment or nearby the home. Cryptococcosis was more frequent among AIDS patients residing in dwellings from which C. neoformans var. neoformans was isolated than among AIDS patients from whose domestic environment the fungus was not demonstrated by the methods used (odds ratio (OR)=2.05). These findings suggest that the distribution of C. neoformans var. neoformans in Rio de Janeiro is not restricted to the classically known biotopes as well as reinforce the possibility of exogenous infection in opportunistic cryptococcosis, including exogenous infection acquired in the domestic environment.