The prevalence of diagnosable psychiatric conditions in any given year is vast - up to 30 percent of the population, in some recent studies. Current health services research suggests that half or more of those who seek help for these conditions look in the general medical sector. Primary care settings and the general medical sector constitute a major part of the official, but defacto, system of care for people with brain-based disorders. How well this defacto system works, and how to make it work better, is a matter of considerable importance. Can primary care physicians - as opposed to mental health clinicians - treat depression, anxiety and other mental health problems effectively? Even if they can, do they have enough time to provide these services in their high-pressure, fast-paced practices? Three frontline experts respond to this critical question: a noted HMO psychiatrist who is implementing depression treatment programs in primary care clinics, a consumer advocate for the federal Center for Mental Health Services, and an ''internist's internist'' who helped create the DSM-IV for primary care, articulate how those on the receiving end of the system need to be part of the planning for these services.