This report covers the initial phase of a longitudinal study of adolescent personality, intended to examine the impact of cultural change on adolescent personality development. The High School Personality Questionnaire (Cattell), the Personality Research Form (Jackson) and the Primary Mental Abilities Test battery (Thurstone and Thurstone) were administered to secondary school students to yield temperament and ability dimensions (only the former is reported on in this intermediate report). Separating ontogenetic (individual) and generational (historical) sources of temporal change was accomplished by application of longitudinal sequences consisting of a series of short-term longitudinal studies, analyzed by Schaie's time-sequential method. The results lend strong support to the argument that, due to potential generational change, cross sectional age gradients are fallacious indicators of true age change. Systematic personality differences were clear between cohorts born but a few years apart. The nature and status of adolescent personality development appear to be dictated less by age-related maturational components than by the type of cultural ecology which is setting the environmental milieu for all adolescents at a given point of time. (KS)