Employed were a small sample of fifth graders to examine techniques for assessing the validity of psychosocial maturity (PSM) and the scales used to measure it. Three validation techniques were examined: (1) Data obtained from self-report scales, teacher ratings, and peer ratings were used to generate three multitrait-multimethod matrices (total sample, boys, and girls), and the criteria outlined by Campbell and Fiske (1959) were applied to examine these matrices; (2) a technique was devised to assess the degree to which independent raters could predict the pattern of relationships among PSM and other scale scores; and (3) PSM subscales were used to generate regression coefficients predicting rated traits. Validity studies in general and some implications for the validation of a new PSM scale are discussed. A major implication for future studies is that validation of component subscales of PSM, rather than of the multidimensional construct as a whole, should be attempted. (Author)