Assessment of the relationship between ontogenetic (individual) and generational (historical) change in adolescent personality development was the focus of this study. The total sample included 1000 male and female adolescents (ages 13-18) randomly drawn from 32 public school systems in West Virginia following a design using longitudinal sequences and control groups. Longitudinal subjects (birth cohorts 1954-1957) were measured in 1970, 1971, and 1972 with Cattell's High School Personality Questionnaire, Jackson's Personality Research Form, and Thurston'es Primary Mental Abilities. A random sample of retest control subjects was measured in 1972 only. Analyses were aimed at examination of main and interaction effects of age/cohort, sex and time of measurement on 16 personality and ability measures and of intraindividual change and stability on these measures from 1970 to 1972. Control group data were analyzed for testing and selective dropout effects. Findings indicated that age per se is not a very relevant variable. Rather, (1) developmental change is more influenced by the cultural moment than by age sequences; and (2) traditional, simple cross-sectional or longitudinal designs are not adequate for describing developmental change. Theorizing about adolescent development must move toward a dynamic conception of "the changing individual in a changing society". This will mandate rapprochement between ontogenetic and evolutionary models of development. (Author)