The acarofauna and Der p I allergen concentrations in dust samples from mattresses and lounge room carpets obtained from 20 homes from two coastal cities, Perth and Bunbury, were determined. All samples were shown to contain mites and the geometric mean numbers of total mites/g of mattress and carpet dust for Perth and Bunbury were 480 and 263, and 585 and 992, respectively. Carpets from both centres had a significantly (P < 0.02) greater mean number of mite species (Perth 9.1, Bunbury 9.0) than mattresses (Perth 5.2, Bunbury 5.7). The predominant mite species were D. pteronyssinus, E. maynei and Tarsonemus spp. D.farinae was found to be absent from all dust samples examined. E. maynei was present in the 10 Bunbury homes and in 50% of the Perth homes, ranging from 0 to 81% of mites identified. The arithmetic mean Der p I concentrations in the mattresses and carpets in Perth and Bunbury were 4.2 and 4.1, and 3.8 and 9.2 μg/per gram of fine dust, respectively, and Der p I concentration correlated with mite counts (r = 0.75; P < 0.001). The concentration of Der p I equivalent per 100 mites was 1.5 μg. The data are consistent with the view that asthmatic patients in Western Australia have significant exposure to a variety of house dust mites and that E. maynei may be clinically significant.