Five measurements of the head were taken between 1 year and 18 years of age in 1,537 North American Caucasians. By 1 year of age, the circumference (87.5%) and length (87.1%) of the head showed the highest levels of developmental level compared with their adult size. By 5 years, the developmental level of all measurements in head width, head length, and circumference increased, closely approaching maturation. Head length reached full maturation at 10 years in females (182.7 mm), and at 14 years in males (189.2 mm). In females, head width showed the most advanced maturation at 14 years (142.7 mm). In males, most of the head measurements matured at 15 years of age. Adult head height was approached at 13 years in both sexes (113.3 mm in males and 109.8 mm in females). Early rapid growth in head height and head length took place between 1 and 4 years of age, and between 1 and 6 years in forehead width. The head width and head circumference showed continuous but mild growth rates throughout this period.