BACKGROUND The North American Primary Care Research Group (NAPCRG) Task Force on Mental Health Problems was commissioned to explore critical research and policy issues in mental health and to develop a primary care research agenda for review and action by NAPCRG. This paper presents the key findings and recommendations of the task force. METHODS As co-chairpersons of the task force, we performed a comprehensive review of the primary care mental health literature using MEDLINE searches with manual follow-up and personal communications with many active researchers in the field. Task force members participated in the editing and refinement of this paper through electronic mail and a series of face-to-face meetings. CONCLUSIONS Rapid changes in the US health care environment threaten to undo the integration of mental and physical health that is at the heart of primary care. It will be necessary for the primary care leaders in the mental health field to step forward to guide policymakers, purchasers, and the public as primary care is reengineered for the next generation. Efforts to use episode of care and comorbidity recording within electronic medical record systems, particularly in cooperation with managed care corporations or primary care research networks, may represent the most effective strategy for promoting the integration of mental health services into primary care. The most promising area for original research may be the exploration of common mental health problems in the context of routine primary care practice.