Volunteers who claimed they were "healthy and normal" and did not reveal any physical or mental abnormality or medication use during brief structured interviews underwent detailed structured interviews with the Schedule for Affective Disorders and Schizophrenia. Diagnoses were based on the Research Diagnostic Criteria (RDC), and family history was determined with the Family History RDC. Of the 121 volunteers, 16.5% met criteria for diagnoses of current mental disorders. Of the 104 without current DSM-III axis I diagnoses, 35.6% had past histories and 39.4% had family histories of mental illness. These results emphasize the need for thorough assessment of "normal volunteers."