BACKGROUND: Environmental living conditions co-sorting with economic status may influence the disease morbidity rate of childhood asthma in ethnic minority urban poor populations. OBJECTIVES: This study was carried out to assess exposure and sensitization to environmental allergens in southeast San Diego children with current asthma-related symptoms and to determine the utility of environmental control measures. METHODS: Children, 9 to 12 years old, with current asthma-related symptoms were identified and enrolled at four school sites. Skin prick testing with aeroallergens was performed, and allergen in collected dust (from mattresses, pillows, and bedroom carpets) was quantified by enzyme immunoassay. Environmental control instruction and products were provided. RESULTS: Of 41 subjects who underwent skin testing, 51.2% were reactive to environmental allergens (39% to mite, 22% to cockroach, and 9.8% to cat). Mean allergen levels for sensitized subjects were: Der p 1 (11 subjects), 18,722 ng/gm dust; Der f 1 (8 subjects), 5345 ng/gm dust; Fel d 1 (3 subjects), 214 ng/gm dust; Bla 1 (8 subjects), 7.15 U/gm dust; and Bla 2 (8 subjects) 7.13 U/gm dust. Environmental allergen exposure levels were not significantly different between sensitized and nonsensitized subjects. Environmental control measures for mite exposure were completed in six homes of sensitized subjects. One month after treatment, allergen levels fell 91.2% for Der p 1, 98.9% for Der f 1, and 88.2% for Fel d 1. One year after treatment, mite and cat allergen levels remained low. Environmental control had no consistent impact on cockroach allergen levels. CONCLUSION: Environmental allergen sensitization and exposure may be cofactors contributing to increased disease severity in urban poor populations. (J ALLERGY CLIN IMMUNOL 1996;98:288-94.)