The revised examination for The Measurement of Efficiency of mental functioning is planned to evaluate the mental efficiency of children and adults in both normal and abnormal mental conditions. Its purpose is not to make a medical diagnosis by giving a name to the condition; but rather to make a psychological diagnosis by determining the mental weaknesses and the available mental assets as a basis for appropriate therapy and guidance.Development of the Method.-Paretic patients who had been judged able to undergo malarial treatment were used in the first experimental work because their mental malfunctioning was attested to by other reliable criteria. The plan was to prove the validity of the examination by the differences between the scores of patients who would later be paroled and the others. The results showed a statistically reliable difference between the normal and paretic patients and also between the ones who were paroled and the ones who were not (1).Statistical validity for the groups, however, was not validity for the individuals who composed the groups. Some patients who had made the lowest scores were later paroled, while others who made relatively high scores were held in the hospital. Study of the history of the cases brought out the fact that low scores were not entirely due to diseased brains and that the paroled patients who scored very low were inferior in native intelligence, as shown also by their school and work histories, while the ones who had rated much higher on the efficiency examination but had been retained in the hospital were superior in potential intelligence as shown by their educational progress and professional careers. These findings led to the now obvious conclusion that scores are not revealing in themselves, but only in relation to norms for persons of the same level of abstract-74 1