OBJECTIVE: The prevalence, burden, and management of insomnia among primary care patients were evaluated. METHOD: Consecutive patients aged 18 to 65 years in primary care clinics of a staff-model health maintenance organization (N = 1,962) were screened with the 12-item General Health Questionnaire. A stratified random sample (N = 373) completed face-to-face diagnostic assessments including the Composite International Diagnostic Interview, a brief self-rated disability questionnaire (Brief Disability Questionnaire), and the interviewer- rated Social Disability Schedule. A telephone follow-up survey was completed 3 months later. Use of psychotropic drugs, use of mental health services, and direct health care costs were assessed by using the health plan's automated data systems. RESULTS: Approximately 10% of the primary care patients reported major current insomnia (e.g., taking at least 2 hours to fall asleep nearly every night). Current insomnia was associated with significantly greater functional impairment (according to both Brief Disability Questionnaire and Social Disability Schedule), more days of disability due to health problems, and greater general medical service utilization. While insomnia was associated with depressive disorder and chronic medical illness, adjustment for these factors only partially accounted for the association of insomnia with disability and with health care utilization. Of the patients with current insomnia, 28% received any psychotropic drug; 14% received benzodiazepines and 19% received antidepressants. CONCLUSIONS: Insomnia among primary care patients is associated with greater functional impairment, lost productivity, and excess health care utilization.