The NEO Personality Inventory-3 (NEO-PI-3) is a modification of the Revised NEO Personality Inventory (NEO-PI-R) designed to be more understandable to adolescents. Data from adults aged 21 to 91 showed that the NEO-PI-3 also functions as well or better than the NEO-PI-R in adults. Age trends from combined adolescent (n = 500) and adult (n = 635) samples confirmed previous cross-sectional findings and demonstrated the importance of studying age changes especially at the facet level and during the decade of the 20s. Normative data for self-report and observer rating forms for adolescents, younger and older adults, and all adults are discussed, as well as for a combined-age group. It is argued that combined-age norms may be most appropriate for depicting the personality scores of individuals, but the utility for some purposes of within-age group scores is also acknowledged.