ABOUT 10 to 60 percent of the people receiving care from a general practitioner or interniist during a year have a significant emotional or psychiatric problem-as perceived by the physician. But how perceptive is the average family physician in detecting mental illness, and what factors influence his perceptiveness? If the family physician is to function as a resource for early detection of mental illness, how must his training be altered? And how would the caseload for all the psychiatric services in a community be affected if the family physician referred all patients in whom he perceived a significant psychiatric problem to a psychiatric service? If we look toward the family physician for psychiatric care, we must know the kind of care he offers and how he must be educated to serve more effectively (1-16). Monroe County, N.Y. (including metropolitan Rochester), population 630,000 in 1964, afforded a unique opportunity for a study to obtain at least a partial answer to many of these questions. A centralized case register of all psychiatric services has been maintained there since January 1960. Almost all psychiatric services, Mr. Locke is acting chief of the center for epidemiologic studies,