Measurement and definition of sexual orientations have increasingly become a central focus in both research design and public policy debates. This paper reviews major methods, and their theoretical underpinnings, for the definition and measurement of sexual orientation, highlighting their limitations and pitfalls, both practical and conceptual. The increasing politicization of this area is discussed and cautioned against. Recommendations, both general and geared toward measurement concerns with adolescent populations, are made. A specific measurement strategy, which can be utilized at a number of different levels, is detailed.