House-dust flora and fauna were compared in the maritime cool temperate climate (in three degrees of continentality), the mediterranean warm temperate climate, the arctic climate and the tropical climate. An inverse relationship exists between continentality of the temperate climate and the numbers of arthropods and fungi (mesophilic as well as xerophilic) in the dust of the houses. The numbers of arthropods and fungi were lowest in mediterranean and arctic climates, most likely because of the limiting effect of the drier indoor climate. Fungi are more tolerant of dry conditions than house-dust inhabiting mites. Generally the highest numbers of fungal diaspores and arthropods were found in the tropics, where, however, the lowest number of positive samples was also found, especially for the species of the Aspergillus glaucus group and for Wallemia sebi. Maritime cool temperate climate showed the highest numbers of positive samples for fungi and mites. In general, a relationship exists between relative humidity and the density of fungal diaspores and arthropods.