To measure Derp1 and Blot5 allergen levels in asthmatics’ homes in Hongkong. Methods Seventy houses were enrolled for a mite indoor environment study. Dust samples were obtained from two sites of each patients’ house: bed and floor. Derp1 and Blot5 levels were quantified by a two-site monoclonal antibody-based ELISA technique. Results The levels of Derp1 allergens found in bed （geometric mean （GM） 3.43 μg/g of dust; 95%CI

1.89-4.96 μg/g） and on the floor （GM 1.12 μg/g of dust; 95%CI

0.71-1.53 μg/g） indicated significant differences （P = 0.005）. However

the levels of Blot5 allergens found in bed （GM 19.00 μg/g of dust; 95%CI

0.89-38.90 μg/g） and on the floor （GM 6.14 μg/g of dust; 95%CI

0.40-11.90 μg/g） showed no statistically significant difference. In addition

in regards to the exposure index for Derp1 and Blot5 allergens found in bed and on the floor

17.6% in bed and 8.6% on the floor had levels of Blot5 ≥ 10 μg/g of dust

higher than those obtained for Derp1 （7.2% and 0% in bed and on the floor respectively

P < 0.05）; higher percentages in bed and on the floor （25.0% and 35.7%） were observed for levels of Blot5 = 0 μg/g of dust as compared with Derp1 in bed and on the floor （4.3% and 14.5% respectively

P < 0.05）. Conclusions Derp1 and Blot5 are the major allergens found in this regional study

Blot5 is a more potent allergen in Hongkong

probably reflecting the high level of exposure to Blomia tropicalis （Bt）. Bt and Dermatophagoides pteronyssinus（Dp） allergens should be included for precise diagnosis and effective immuno-therapeutic treatment of mite allergy in Hong-kong.