The Akerfeldt test for serum-oxidase activity, originally proposed as a test for mental disease, should not be used for that purpose. Sera yield "normal" or "abnormal" results depending on the temperature and pH at which the reaction is carried out. Even when the method is standardized to eliminate these 2 variables, the results obtained depend so greatly on the subjects'' previous diet that they render the- test of questionable value in the diagnosis of anything, except perhaps ascorbic acid deficiency.