The qualitative and quantitative species composition of fungi in carpets and upholstered furniture dust found in the living-rooms of nine Dutch dwellings was examined in a pilot study. Numbers of spores of xerophilic fungi did not differ in dust removed from carpeting' and upholstery. Spores of hydrophilic species were found to be more predominant on floors (P < 0.05), whereas meso-hygrophilic spores, largely dominated by allergologically relevant Penicillium species, were significantly more abundant in dust taken from regularly used furniture (P < 0.05), Our results indicate that growth conditions for fungi in the micro-habitats of furniture differ from those in carpeting. No statistically significant differences in number of viable spores have been found in samples taken from ground-floor level compared with those taken from 1st to 3rd floor level of dwellings. From this study, the need for a micro-topographic analysis of the fungal flora in the human environment has become apparent. Efficient allergological home sanitation in dwellings of allergic patients requires detailed data about the colonization of the various micro-habitats by allergenic fungi.