Background: Previous studies have shown that asthma education and case management may reduce asthma emergency care, hospitalizations, and expenditures. Objective: We sought to study the effect of an asthma outreaeh program (AOP), a team-based, case-management intervention, on emergency ward (EW) and hospital use. Methods: Fifty-seven patients aged 1 to 15 years with the diagnosis of asthma based on the usual clinical practice criteria who ere continuously enrolled in a staff-model health maintenance organization for a period of at least 2 consecutive years were randomized into 2 intervention groups. The control group received a single intensive asthma education intervention, and the BOP group received the same initial education hut then was followed-up by an asthma case management nurse throughout the intervention period. Results: EW visits, hospitalizations, and total outside-of-health-plan expenditures (consisting of EW and hospital expenses, as well as miscellaneous costs, such as ambulance, durable medical equipment, tertiary referrals, and home care) were assessed from claims pled for a year before and after enrollment. Control group patients experienced significant reductions in EW visits (39%), hospitalizations (43%), and outside-of-health-plan costs (28%), possibly as a result of the baseline educational intervention received by all enrolled patients, in conjunction with regression to the mean. AOP group patients experienced significant reductions in EW visits, (73 %, P = .0002), hospitalizations (84% p = .0012), and outside-of-health-plan use (82%, P < .0001), When compared with the control group, AOP group patients demonstrated additional significant reductions in EW visits (57%, P < .05), hospitalizations (75%, P < .05), and outside-of-health-plan use (71%, P < .001). Estimates of direct savings to the health plan ranged from $7.69 to $11.67 for every dollar spent on the AOP nurse's salary, depending on assumptions, Conclusions: Asthma patients in a staff-model health maintenance organization decreased their resource use between 57% to 75% by participation in an AOP as compared with a randomized control group receiving only an educational intervention. Substantial savings were achieved compared with the cost of the AOP nurse.