The importance of ''self-management'' has been increasingly recognized in the treatment of asthma. In the case of childhood asthma, such management must be accomplished by the family system, including the caregivers, the asthmatic child, and the alternate caregivers in collaboration with the health care providers. This paper presents an assessment tool, the Family Asthma Management System Scale (FAMSS), for evaluating the effectiveness of the family asthma management system. The scale is internally consistent and has excellent interrater reliability. The FAMSS score, together with an asthma severity measure, jointly accounted for a significant portion of the variance when predicting the functional severity of asthma experienced by this group of children.