Few topics in sexology elicit such a diversity of opinions and emotions as the question of etiology of homosexuality. Views frequently carry with them implicit or explicit messages concerning the psychologic health of this sexual orientation. Theories of sexual development usually portray adolescence as a critical time in the life course because of changes in: 1) anatomy and physiology; 2) psychologic functioning: the reawakening, renewal, and reliving of previously established sexual relations and drives; and/or 3) social conditions: an increased exposure and adherence to societal messages concerning appropriate and inappropriate social and sexual behaviors and relationships. This paper provides a brief overview of several major theories--evolutionary biology, psychoanalysis, and social processes--as they relate to the development of sexual orientation. In addition, an ethologic perspective that synthesizes various etiologic theories, as they relate to homosexuality during adolescence, is briefly reviewed. In these discussions, the issue of whether homosexuality is a normal or abnormal developmental state during adolescence is also addressed.