Each generation of adolescents is exposed to a wider array of stressors and environmental deficits. Use, abuse, and dependence on alcohol and other drugs greatly impairs youths' ability to develop fully, and exacerbates and compounds other biopsychosocial problems. Physiologically, the onset of secondary sex characteristics, the growth spurt, final development of the central nervous system, as well as hormonal, neurotransmitter, and biochemical changes occur during adolescence. Mood altering chemicals alter human physiology including neurotransmitters. Young people who use chemicals also have a more difficult time with psychological tasks, such as individuation, emancipation, and separation. Their relationships with families tend to be marked by conflict and polarized feelings. Adolescence is also a period of development of a gender role identity or integrating sexual impulses into self concept. Young people who use chemicals are more likely to have difficulty controlling impulses and have high rates of promiscuity and prostitution. Another developmental area common to adolescence is the development of a moral code. Young people who use chemicals tend to become involved in behaviors viewed as anti-social, including theft, selling chemicals, and sexual misadventure. Career choice is another developmental area of concern. Because prospects for well paying jobs are limited as compared to the past, some young people take a fatalistic approach toward their education. The progression of chemical use, risk factors, and an overview of evaluation and intervention techniques and strategies are presented. (LLL)