To evaluate the cost-effectiveness of a "fast track" system for diverting lower acuity patients away from the pediatric emergency department (ED), 4,060 patients triaged to the fast track area of an urban pediatric ED with the 10 most common discharge diagnoses from 1/1/94 through 12/31/94 were retrospectively evaluated. Patients triaged as having nonurgent concerns qualified for treatment in a separate fast track area for 8 hours per day (fast track patients). These patients were compared with 5,199 seen in the main pediatric ED for the same concerns during the remaining hours when the fast track was not in operation (ED patients). Computer records were reviewed for demographics, acuity levels, diagnosis, and collection ratios (revenues/charges). The societal savings was calculated as sigma $ [(delta mean revenue of diagnosis1-10 in the main ED - mean revenue of diagnosis1-10 in the fast track) x the number of patients seen in fast track for diagnosis1-10] stratified by acuity. Collection ratios were comparable between groups (57% v 62%), but the average charges (physician and facility) were significantly less for patients seen in the fast track by a ratio of 1:2.4 (P < .0001). The average net revenue was also significantly less for all patients seen in the fast track by a ratio of 1:2.6 (P < .0001). When stratified by diagnosis and acuity, the savings to society was $101,313, or an average of $25/patient seen in the fast track ($101,313 per 4,060). A fast track is an effective system for maintaining patient flow at a cost savings to society. It can help the hospital in its negotiations with payors because it curtails charges. It is also a potential means for maintaining overall departmental revenues as payors increasingly deny traditional pediatric ED visits for patients with lower acuity concerns.