The Dermatophagoides mites are well recognized as allergens in bronchial asthma. A survey of mattress dust in Birmingham showed large numbers of Euroglyphus maynei to be present in addition. A variation was found in mite populations in dust collected by vacuum cleaner when compared to brushed samples, which may explain previous findings of only small numbers of E. maynei. A mean density of 296 pyroglyphid mites; 100 μg dust was found in mattress dust. Glycyphagus species formed only 1%, of all mites seen.