The study concluded that M3 development as a means of estimating age for late teens and young adults should be used with caution because of the broad age range within each Demirjian stage for either American Blacks or Whites. Even the ability to determine whether an individual was legally an adult by assessing M3 development was significantly limited. Statistically, the most significant study finding was the comparatively large difference between American Blacks and Whites, with Blacks maturing faster as measured by M3 development, at least during adolescence. Most median differences exceeded 1 year. The mineralization of M3s, unlike other teeth, was found to be faster in White males than White females. The opposite was true for American Blacks. Data for Whites were collected from several dental practices and treatment facilities across the United States and Canada. Most of the data for Blacks, however, were collected from the University of Tennessee College of Dentistry, a private orthodontic office in Memphis, TN, and an Arkansas penal facility. The formative status of the M3 was assessed in each quadrant. Both the left and right sides in both arches were scored when possible. Most data were collected from panoramic radiographs, although periapical views (with finer resolution) were used when available. The eight-grade scheme of Demirjian was used to classify the stage of M3 development. A preliminary training session was held for the purpose of standardizing examiner grading. In each instance, the stage judged "closest" was recorded. 4 tables, 3 figures, and 28 references