A significant correlation exists between mite allergen exposure levels and asthmatic attacks of the mite allergic patients. It is very important to measure the allergen levels in the environment. House dust mites and major allergen levels of Der p 1 and Der f 1 in pillow and mattress dust in Shanghai were detected with monoclonal antibodies by biotin-avidin ELISA. Dermatophagoides pteronyssinus was the predominant species in pillows and mattresses in Shanghai. The levels of Der p 1 were high in bedding dust samples in this area. The density of D. farinae was very low and Der f 1 was negligible. It is important to monitor the density of D. pteronyssinus. Reduction of the density of house dust mites and their allergen levels in patient's houses has the potential to reduce the incidence of risk of asthma attacks.