[영문]OBJECTIVE: This study sought to determine whether an intervention for patients with medically unexplained symptoms in primary care reduced total costs, components of cost, and longer-term costs and whether it led to decreased service use outside the health maintenance organization (HMO). METHOD:S: A randomized controlled trial involving 206 patients with medically unexplained symptoms was conducted in a staff-model HMO. The protocol emphasized the provider-patient relationship and included cognitive-behavioral therapy and pharmacological management. Cost data for medical treatments were derived from the HMO's electronic database. Patients were interviewed about work days lost and out-of-pocket expenses for medical care outside the HMO. RESULTS: The difference in total costs (