The purpose of this study was to explore changes in adolescent self-presentation on the Minnesota Multiphasic Personality Inventory (MMPI; Hathaway & McKinley, 1940) and MMPI-A (Butcher et al., 1992) over a 40-year period. The primary samples used for comparison in this study include 1,235 adolescents, age 14 through 16, derived from the MMPI-A normative sample (Butcher et al., 1992) collected in 1989 and 10,514 adolescents, age 14 through 16, collected in 1948 and 1954 from Hathaway and Monachesi's (1963) study of adolescent personality and behavior. MMPI basic scale and item-level data were also included for 817 adolescents, age 14 through 16, collected by Colligan and Offord (1992) in 1985 as a further comparison. Between-sample analyses at the profile level revealed that adolescents from the MMPI-A normative sample scored significantly higher across basic clinical scales and lower on validity scales L and K than adolescents from the Hathaway and Monachesi (1963) sample, with mean data from the Colligan and Offord (1992) sample typically falling at a midpoint value. Analyses of Harris-Lingoes (Harris & Lingoes, 1955) subscale and item-level data were conducted to provide refined definitions of the contents of scale-level changes. Results were interpreted as reflecting moderate to large changes in response frequencies between eras of data collection, and emphasis was placed on the relatively high frequency of item endorsements by contemporary adolescents in the clinical direction in the MMPI-A normative sample. A series of cautions and limitations are also offered in interpreting these patterns.