BACKGROUND Dermatophagoides pteronyssinus and Euroglyphus maynei frequently occur in house dust but little is known about primary sensitization to the less abundant E. maynei. OBJECTIVE To determine the occurrence of primary sensitization to E. maynei by T-cell responses and the crossreactivity to D. pteronyssinus. METHODS The proliferative response of peripheral blood cells to overlapping peptides from Der p 1 and Eur m 1 were measured as well as to peptides from Der f 1, an allergen not found in the study environment. RESULTS The most frequent and strongest responses were to Der p 1 peptides especially in the region 105-133. However, 3/17 responders to mite peptides were stimulated predominantly by Eur m 1 peptides and a further two had their highest response to an Eur m 1 peptide. There was very little crossreactivity between Der p 1 and Eur m 1 peptides and very little response to peptides from Der f 1. CONCLUSIONS E. maynei group 1 allergens are a significant source of primary T-cell sensitization and have little T-cell crossreactivity with D. pteronyssinus or D. farinae.