In the lesbian community, one which based upon a shared sexual minority identity, recent attempts to add the category to the prevailing dichotomous conceptualization of sexuality have led to various popular conceptualizations of sexuality. Lesbian-identified women disagree among themselves and with bisexual-identified women over whether bisexuality exists, and if so, what it is. As a result, individuals develop lesbian and bisexual identities based on differing conceptions of sexuality, thereby undermining the basis for affiliation among women with a shared sexual identity. This paper, based upon data from 365 lesbian- and bisexual-identified women who were questioned about their sexual identity histories, behaviors, and feelings of sexual attraction, demonstrates that while there are aggregate differences between the experiences of lesbian and bisexual women, there is also a wide range of sexual experience common to both groups. The paper argues that the tension which characterizes relations between lesbian- and bisexual-identified women is not the result of failure to recognize these similarities in experience. Instead, historical circumstances have led to a situation in which bisexuality poses a personal and political threat to lesbians and lesbian politics; the similarity between lesbians' and bisexuals' experiences aggravates rather than mitigates this threat. The existential question Who am I? has proved troubling to generations because it is paradoxical. The question ostensibly asks for a description of one's essence, a quality discovered only through the evidence of personal experience. Social constructionist theory points out, however, that individuals interpret their personal experiences through the framework provided by the social world. From the viewpoint of the individual, identity is discovered by introspection. But from the viewpoint of the social constructionist, identity is a construct reflecting the conceptual structure of the surrounding social world. While the production of identity is a social-psychological process, the consequences of identity are both social and political. This is especially true when identity reflects membership in a disadvantaged or stigmatized group such as a racial, gender, or sexual minority. Members of these minorities form sociopolitical communities based upon shared identity. Feelings of belonging and solidarity arise within minority communities, based upon the belief that members share a common experience which leads to shared interests and values. Eventually, minority communities become politicized and build social change movements that are also based upon the belief that shared identity reflects shared experiences and interests. The belief in common experience underlying the formation of minority communities hinges on the assumption that all individuals have interpreted their experiences through the same conceptual structure. If different individuals interpreted their experiences through different conceptual structures, shared identity would not reflect shared experience. Communities based upon shared identity would include individuals with a wide range of experiences, and the experiences of community members would overlap the experiences of nonmembers. The original purpose of establishing a minority community-bringing together individuals with similar experiences and interests-would be undermined.