The Myers-Briggs Type Indicator is a self-report inventory which is intended to measure four variables stemming from the Jungian personality typology: extraversion-introversion, sensation- intuition, thinking-feeling, and judging-perceiving. The construct validity of each of its scales was assessed in a series of studies which investigated the content of the scales, their correlations with ability, interest, and personality scales, and differences on the scales associated with sex and high school program. The findings suggest that the Sensation-Intuition and Thinking-Feeling scales may reflect restricted aspects of the dimensions that they are intended to represent, and the Extraversion-Introversion and Judging-Perceiving scales may reflect something quite different from their postulated dimensions.