A subset of members of the Hathaway and Monachesi (1953, 1961, 1963) normative adolescent MMPI dataset was examined to find MMPI scales that predict the future onset of schizophrenia or adult psychopathy. The sample consisted of 23 individuals who later developed schizophrenia, 30 individuals who later developed psychopathy, and their matched controls. Results suggested that nine MMPI scales could reliably distinguish between schizophrenia and no schizophrenia; an additional nine scales could distinguish between adult psychopathy and no psychopathy. These 18 scales could also be used to discriminate those individuals who later developed schizophrenia from those individuals who later developed psychopathy. The results support the hypothesis that latent personality characteristics can function as endophenotypes for some adult psychopathologies.