The purpose of this investigation was to examine within-group differences among self-identified sexual orientation and identity groups. To understand these within-group differences, 2 types of analysis were conducted. First, a sample of 2,732 participants completed the Sexual Orientation and Identity Scale. Cluster analyses were used to identify 3 types of bisexual women, 3 types of bisexual men, 2 types of heterosexual women, and 2 types of gay men. Lesbians and heterosexual men were clustered into singular groupings. In addition, a subsample of 838 participants also completed measures of sexual identity development and lesbian, gay, and bisexual knowledge and attitudes. Within-group differences were found for bisexual men and women, gay men, and heterosexual women along these dimensions. Findings supported the existence of distinct subgroups of bisexual men, bisexual women, gay men, and heterosexual women. (Contains 4 tables.)