Adolescent-specific drug treatment units were initially instituted because it was and still is generally assumed that young people will do better in units tailored to their "unique" interests. The creation of such units assumes that teens have different developmental tasks and life crises than adults, which requires different treatment approaches. Another assumption is that adolescents require family involvement for positive treatment outcomes to occur. A further assumption is that adolescents need peer support and may feel alienated on adult wards; and another assumption is that all teens with psychopathological and behavioral problems (of which drug abuse and dependence are included) should be treated together because their age-related problems make them a homogeneous target population. An analysis of research in several disciplines concerning outcome studies related to adolescent chemical dependency and mental health treatment shows that heterogeneous (multigenerational) treatment settings may be superior to homogeneous age group treatment. Other adolescent issues in the family and society that directly affect treatment philosophies in centers directed toward youth are compared to the treatment philosophies of adult centers. Multigenerational treatment facilities cost less, require less staff, are better received by the client, and produce higher abstinence rates than adolescent-specific centers. 69 references