The Asthma Therapy Assessment Questionnaire (ATAQ) for children and adolescents was developed to assist clinicians and health plans to identify children at risk for adverse outcomes of asthma. ATAQ is a brief, 20-item parent-completed questionnaire that generates indicators of potential care problems in several categories, including symptom control, behavior and attitude barriers, self-efficacy barriers, and communication gaps. This paper describes testing of the internal consistency and construct validity of the instrument. A cross-sectional mail survey with telephone follow-up was conducted with parents of 434 children aged 5-17 years being treated for asthma and enrolled in three managed care organizations in the Midwestern and Northeastern United States. ATAQ scales were evaluated using correlations with measures of health status, asthma impact, and healthcare utilization. ATAQ demonstrated good internal consistency and the hypothesized relationships to corresponding measures from existing instruments. Asthma control was significantly associated with measures of physical health, psychosocial health, resource use, and family impact. "Shared decision making," an indicator of patient-provider communication and involvement of the parent and child in developing asthma management plans, was significantly and positively associated with symptoms and parental satisfaction. Other ATAQ components showed similar associations. ATAQ appears to have satisfactory measurement properties and is ready for use to identify patients who might benefit from further disease management efforts or medical attention.