Many psychiatric symptoms have been described in pernicious anaemia, including depression, manic excitement, paranoid states, confusional episodes, and dementia. Although vitamin B12deficiency is known to produce neurological symptoms there is much less certainty about its role in producing mental symptoms. Despite this uncertainty, it has been asserted that carrying out vitamin B12assays on psychiatric patients will enable doctors to cure for good severe disabling disease which otherwise may end in chronicity (Edwinet al., 1966). Routine examinations to exclude pernicious anaemia have been advocated for all psychiatric patients (Strachan and Henderson, 1965; Hunter and Matthews, 1965). A prudent preliminary is a critical evaluation of the causal relationship between vitamin B12deficiency and individual psychiatric syndromes.