This comprehensive overview of research, issues, and theories relating to sexual orientation, behavior, and identity by experts in various disciplines is unique in providing both historical perspectives and a synthesis of the recent advances in understanding homosexuality and heterosexuality.Drawing from biological and psychological research, this handbook critically reviews the major theories about sexual orientation and examines each theory on the basis of empirical support. One section summarizes recent developments in genetic and neuroanatomic research. Another section discusses problems with sexual performance among heterosexual, homosexual, and bisexual persons. A third section provides overviews of clinical disorders or sexual deviations. Various chapters clarify the distinction between sexual disorders, such as pedophilia, and sexual variations, such as homosexuality. Chapters also examine important social issues relevant to sexual orientation, such as disability, prejudice, aging, and gender roles. Experts address the continuing controversy over the feasibility of altering sexual orientation, new developments in treating different types of problems, and changing perspectives today. This handbook is designed for the use of educators, students, and researchers in the social and behavioral sciences.