On Lok Lifeways (On Lok), the original Program of All-inclusive Care for the Elderly (PACE) organization provides comprehensive health care for community dwelling frail seniors in San Francisco and South Bay areas, California. On Lok serves over a thousand participants who speak 30 languages. Prior to 2005, On Lok did not have an on-site mental health component and participants were referred to off-site contracted psychiatrists and psychologists for all mental health services. In 2005 On Lok introduced an on-site Mental and Behavioral Health (MBH) team. Currently the team includes a neuropsychologist, five psychotherapists and two part-time psychiatrists. In addition, a full time chaplain is assisting participants with their spiritual needs. The goal of the MBH program is to increase interdisciplinary team effectiveness in care of frail elders with mental and behavioral health issues and to improve access to mental health services for a vulnerable and diverse senior population. MBH team members are providing various direct and indirect services to On Lok participants and staff. Key responsibilities include assessment of mental and behavioral health needs for applicants or new enrollees; routine reassessment every 6 months for participants with a psychiatric diagnosis; counseling to participants and their family members; administration and interpretation of neuropsychological tests for participants with cognitive impairments; crisis intervention and management; and psychotropic medication management as requested by primary care providers. In addition, mental health clinicians conduct regular trainings for all staff regarding various mental health and spiritual issues. Implementing on-site MBH services resulted in quadrupling of the number of appointments to mental health clinicians. There was a reduction in psychiatric inpatient utilization from 12 admissions/1000 patients/year in 2004, to 3 admissions/1000 patients/year in 2005. This reduction was sustained over the past 8 years. The availability of MBH clinicians who can provide timely consultations significantly increased interdisciplinary team understanding of mental health issues and increased team confidence in dealing with difficult mental health cases in an outpatient setting. Inclusion of mental and behavioral health clinicians on geriatric interdisciplinary care teams increased the complexity of care coordination; however the integration of mental health component into comprehensive geriatric care improved the quality of care by increasing timely access to mental health services, reduced the rate of psychiatric inpatient admissions, and reduced anxiety and stress of interdisciplinary teams caring for frail elders with mental health diagnoses.