BACKGROUND: Somatization and hypochondriacal health anxiety are common sources of distress, impairment, and costly medical utilization in primary care practice. A range of interventions is needed to improve the care of these patients. OBJECTIVE: To determine the effectiveness of two cognitive behavioral interventions for high-utilizing, somatizing patients, using the resources found in a routine care setting. DESIGN: Patients were randomly assigned to a two-step cognitive behavioral treatment program accompanied by a training seminar for their primary care physicians, or to relaxation training. Providers routinely working in these patients' primary care practices delivered the cognitive behavior therapy and relaxation training. A follow-up assessment was completed immediately prior to treatment and 6 and 12 months later. SUBJECTS: Eighty-nine medical outpatients with elevated levels of somatization, hypochondriacal health anxiety, and medical care utilization. MEASUREMENTS: Somatization and hypochondriasis, overall psychiatric distress, and role impairment were assessed with well-validated, self-report questionnaires. Outpatient visits and medical care costs before and after the intervention were obtained from the encounter claims database. RESULTS: At 6 month and 12 month follow-up, both intervention groups showed significant improvements in somatization (p< 0.01), hypochondriacal symptoms (p<0.01), overall psychiatric distress (p< 0.01), and role impairment (p<0.01). Outcomes did not differ significantly between the two groups. When both groups were combined, ambulatory visits declined from 10.3 to 8.8 (p=0.036), and mean ambulatory costs decreased from $3,574 to $2,991 (p=0.028) in the year preceding versus the year following the interventions. Psychiatric visits and costs were unchanged. CONCLUSIONS: Two similar cognitive behavioral interventions, delivered with the resources available in routine primary care, improved somatization, hypochondriacal symptoms, overall psychiatric distress, and role function. They also reduced the ambulatory visits and costs of these high utilizing outpatients.K E Y W O R D S : co g n it i v e b e ha v i or t h e ra p y ; so m a t i z a t i o n; hypochondriasis; medical utilization; medical care costs.