The report advises that sexual behavior may be of security concern when it is criminal; when it is compulsive, out of control, or indicates a personality disorder; when it exposes the individual to pressure or coercion; or when it is notorious. Sexual behavior provides a significant window into an individual's psyche, so it may also serve as an indicator of broader emotional problems. The bulk of this report provides background information on the nature, causes, and prevalence of a wide variety of sexual behavior. It then discusses security concerns that may or may not be associated with these behaviors. Also addressed are the origins of homosexuality; research is cited to show that being homosexual does not predispose a person to unreliability, disloyalty, or untrustworthiness. Homosexuality does not in itself reflect poor judgment, nor is it an emotional disorder. To the extent that it is concealed, homosexuality may cause a person to be vulnerable to threats of exposure, but not necessarily more so than the adulterer or any other person who conceals an embarrassing personal secret. Sexual orientation alone, therefore, is not an appropriate basis for security concern. Findings in this report suggest a need to rethink criteria for evaluating a number of forms of atypical sexual behavior, some of which may be unrelated to security risk. The report reinforces the importance of case-by-case judgments rather than automatic disqualification of some categories; this emphasizes the need for qualified medical expertise in making many of these judgments. 4 tables and 167 references