The recent increase in asthma morbidity is of major public import and its reduction is a US Public Health Service Objective for the Year 2000. This study will test the cost-effectiveness of recently developed practice guidelines (National Asthma Education Program) designed to reduce asthma morbidity among children. This 4.5-year study implements a randomized controlled clinical trial at three clinical sites. The trial is designed to examine two intervention strategies. The first intervention will determine the effectiveness of an opinion leader training program utilizing principles of academic detailing to maximize guideline adherent prescribing practices (specifically, use of anti-inflammatory medications for children on chronic bronchodilator therapy.) The second intervention will examine the effectiveness and cost-effectiveness (in terms of costs per symptom-free day gained) of organizational change in primary care that is consistent with comprehensive adoption of the national guidelines. It is anticipated that the study arms will substantially differ from usual care in both marginal costs and marginal effectiveness. The primary outcomes to be examined in this study are based on symptom assessment, however, other outcomes, specifically functional status, health care utilization, and patient satisfaction will be examined as well. This PORT-II will determine the effectiveness, and cost-effectiveness of widely distributed guidelines for the care of childhood asthma. If effective, implementation of these interventions could have significant impact on the lives of children with asthma. In addition, this PORT-II will test new educational and organizational approaches to changing practice patterns within managed care organizations. These approaches, if successful, could be applied to a variety of other adult and pediatric health conditions.