A pair of MZ twins with diagnoses of chronic simple schizophrenia has been studied from the genetic, social, medical, and psychiatric standpoint by members of the several professions. Clinical psychologists studied the patients independently and on the basis of psychometric and projective tests found a remarkable similarity in personality profiles. An in-depth family study failed to reveal any evidence of psychiatric disease in other relatives. Consanguinity was absent. The family unit is typical of that described frequently for a schizophrenogenic household, i.e., dominant mother, passive father. Genetic etiologies are discussed in context with occurrence of schizophrenia in MZ twins in this particular family setting.