Six-month utilization data are presented for the mental health unit of a comprehensive neighborhood health center. Almost 5% of the 16,877 people in Charlestown, Mass., used these services at a rate of 48.7 per 1,000 residents. Nearly all the residents of this Boston neighborhood were white; the median family income was $8,828 annually; and 14% of the families received public assistance. Age, sex, marital status, census tract of residence, and diagnostic factors were quantitatively related to the use of services. Those 0-17 years represented 39.6% of the total caseload and had a utilization rate of 57.0 per 1,000. Boys and women were the biggest users of service, and married adults constituted 47.7% of the adults using the service. About 55% of the patients paid through Medicaid. During the study period 999 diagnoses were recorded for 822 separate patients, or 1.2 diagnoses per patient. Findings from the center's caseload are compared with utilization data for other mental health services and available national data. The study data demonstrate that the health center's goals of providing accessible, family-oriented, comprehensive mental health services that are targeted particularly to the lower socioeconomic groups in the community were largely accomplished.