This chapter assesses the distinctive features of female same-sex sexuality and considers their implications for modeling the nature and development of female sexual orientation. After reviewing the state of current research on these directions, it outlines some of the most provocative and promising directions for future research. Of all of the preconceptions about sexual orientation that have been questioned and revised over the years, one of the most important is the presumption that female and male sexual orientation are parallel phenomena, with the same origins and outcomes. To the contrary, women's greater propensity for nonexclusive, fluid patterns of attraction suggests the possibility that the underlying determinants of female same-sex sexuality may be quite different from those for men, requiring different explanatory models.