In the context of a longitudinal study of cognitive and personality development, I examined various correlates of spatial visualization ability, as measured by Vandenberg's Mental Rotations Test, in order to elaborate the meaning of the known sex difference on this factor. Spatial visualization ability in females was correlated with verbal IQ and various aspects of personality. These relations were absent in males. Within each sex, measures of cognitive abilities obtained in childhood predicted spatial visualization ability at age 18. Hypotheses designed to explain the sex difference in spatial visualization must be sensitive to the different implications of this factor in males and females. (PsycINFO Database Record (c) 2016 APA, all rights reserved)