Numerous developmental changes occur across levels of personal organization (eg, changes related to puberty, brain and cognitive-affective structures and functions, and family and peer relationships) in the age period of 10 to 15 years. Furthermore, the onset and escalation of alcohol use commonly occur during this period. This article uses both animal and human studies to characterize these multilevel developmental changes. The timing of and variations in developmental changes are related to individual differences in alcohol use. It is proposed that this integrated developmental perspective serve as the foundation for subsequent efforts to prevent and to treat the causes, problems, and consequences of alcohol consumption. D URING THE DEVELOPMENTAL period spanning 10 to 15 years of age, considerable changes occur in biological, cognitive, emotional, and social processes, as well as physical and social contexts. These changes occur across different levels of personal organization, including overt physical appearance (eg, increases in physical size), refinements in the structure and function of the central nervous system (CNS), and maturational changes in the internal hormonal and neurophysiological milieus. By age 10, most adolescents have begun the rapid changes of puberty, as defined by changes in secretory patterns of the gonadal steroids. These hormonal changes are accompanied by dramatic changes in height as well as readily visible changes in body composition and secondary sexual characteristics, with overt physical differences between the genders becoming increasingly apparent.Whereas some personal changes are closely aligned with chronological age, such as attendance at elementary, middle, or high school, others are more closely tied to variations in the timing of events (pubertal onset) and/or developmental stages, such as interest in the opposite gender and relative peer influences. As a result, different aspects of personal development take place at different times, and different individuals mature in different dimensions at different times. For example, pubertal development may occur at a different time than does the socialcognitive development necessary for intimate relationships. The physical and emotional changes associated with pubertal development occur over a considerable age range. Adolescents who begin puberty relatively early may experience processes postulated to be associated with puberty, such as heightened emotional states and greater influences of external stimuli, sooner than they have the cognitive and emotional abilities to control consistently behaviors that develop as a function of the maturation of brain regions and collaborative brain networks.The average age of puberty has decreased over the past century, whereas the average age of assumption of adult roles has increased because of prolonged education by more youths and later age of initial marriage. These changes have heightened the significance of understanding adolescence along the multiple continua of physical, cogniti...