The limitations and validity of psychiatric diagnosis, especially as it pertains to medicolegal cases, are discussed. Two clinical cases are used to demonstrate some of the problems. Two young black men were facing charges of murdering a woman; in one case the victim was not a relation and in the other she was the subject's mother. During the period of observation no hard signs of psychosis could be demonstrated, yet the second subject later became overtly psychotic, while the first was and remained normal. Suggestions about diagnostic procedures are made.