The goal of this investigation was to use a community-based participatory research approach to develop, pilot test, and administer an asthma screening questionnaire to identify children with asthma and asthma symptoms in a community setting. This study was conducted as the recruitment effort for Community Action Against Asthma, a randomized trial of a household intervention to reduce exposure to environmental triggers of asthma and was not designed as a classic prevalence study. An asthma screening questionnaire was mailed and/or hand delivered to parents of 9,627 children, aged 5 to 11 years, in two geographic areas of Detroit, Michigan, with predominantly African American and Hispanic populations. Additional questionnaires were distributed via community networking. Measurements included parent report of their child's frequency of respiratory symptoms, presence of physician diagnosis of asthma, and frequency of doctor-prescribed asthma medication usage. Among the 3,067 completed questionnaires, 1,570 (51.2% of returned surveys, 16.3% of eligible population) were consistent with asthma of any severity and 398 (12.9% of returned surveys, 4.1% of eligible population) met criteria for moderate-to-severe asthma. Among those meeting criteria for moderate-to-severe asthma, over 30% had not been diagnosed by a physician, over one half were not taking daily asthma medication, and one quarter had not taken any physician-prescribed asthma medication in the past year. Screening surveys conducted within the context of a community-based participatory research partnership can identify large numbers of children with undiagnosed and/or undertreated moderate-to-severe asthma. These children are likely to benefit from interventions to reduce morbidity and improve quality of life.