The decade between 1998 and 2008 saw rapid increases in research on adolescent sexual orientation development and related health issues, both in quantity and in quality of studies. While much of the research originated in North America, studies from other countries also contributed to emerging understanding of developmental trajectories and social influences on the health of sexual minority adolescents. This paper reviews the body of research from the past decade on adolescent sexual orientation, focused on issues of measurement, developmental trajectories, evidence related to health disparities, and the risks and protective factors that help explain the health and developmental challenges some lesbian, gay, and bisexual adolescents experience. Although many sexual minority adolescents face stigma and rejection within their families, their schools, or their communities, it should be noted that most successfully navigate the developmental tasks of adolescence, and attain similar levels of health and well-being as their heterosexual peers, often despite the stigma and discrimination they encounter. Further research is needed to understand population trends as well as individual patterns of development; cultural variations in both development and health disparities; the interplay of general and unique risk factors that contribute to various health disparities and protective factors that buffer those risks; and interventions to promote the healthy development of sexual minority adolescents.