The present research assesses adolescent personality maturation by examining 3 measures of change and stability (i.e., mean-level change, rank-order stability, and profile similarity) of Big Five personality traits, employing data from a 5-annual-wave study with overlapping early to middle (n = 923) and middle to late (n = 390) adolescent cohorts. Results indicated that mean levels of Agreeableness and Emotional Stability increased during adolescence. There was mixed evidence for increases in Extraversion and Openness. Additionally, rank-order stability and profile similarity of adolescent personality traits clearly increased from early to late adolescence. For all change facets, the authors found evidence for gender differences in the timing of adolescent personality maturation, as girls were found to mature earlier than boys.