The California Test of Mental Maturity is one of the newer intelli gence tests which has attracted wide attention within the last year or two. An important reason for the interest in it is that it attempts to make a diagnostic measurement of mental functions. The test is designed to measure the following types of mental ability : memory, spatial re lationships, reasoning, and vocabulary. Each of these parts contains several sub-tests. The test yields three intelligence quotients?an IQ for language factors and an IQ for non-language factors, as well as the usual type of IQ based on total scores. The IQ for language factors is based on tests of delayed recall, number quantity, inference, and vocabu lary. The IQ for non-language factors results from tests of immediate recall, sensing right and left, manipulation of areas, foresight in spatial relations, opposites, similarities, analogies, number series, and number quantity.