SummaryA survey of the house dust mite population was carried out in the homes of fifty asthmatic Liverpool individuals with strongly positive skin tests toDermatophagoides pteronyssinus.As expected,D. pteronyssinuswas the commonest species found. However,Euroglyphus mayneimade up 37% of the total adult mite count and was the predominant species in 48% of beds examined. There was a good correlation between increasing numbers ofE. mayneiand decreasing social class, but only a weak one with percentage relative humidity. Ionic sodium levels in bed dust were found to correlate with decreasing social class and increasingE. mayneilevels. In nineteen beds, mites were sampled at 4‐monthly intervals for 1 year—this showed a relative decrease in the proportion ofE. mayneicompared with other mites in the autumn, when relative humidity was high. A further twenty beds underwent intensive house dust eradication (including the use of plastic covers) for 1 year—these beds showed a progressive fall in the proportion ofE. mayneirecovered, suggesting that this mite is more vulnerable to anti‐house dust mite measures.Euroglyphus mayneiis a common house dust mite and further work needs to be done to assess its antigenic nature and clinical signi