Motivations of low-income substance using heterosexual Black women in New York City for having multiple sexual partners are explored in this paper. Analysis of in-depth interviews with 50 study participants demonstrates that their relationships consisted of those who had: (1) a main sex partner and a secondary sex partner; or (2) two or more "casual" partners. Individual-level motivations for extra relational sex fell into four dominant themes: sexual pleasure, partner infidelity, sex exchange and past main partners. Using a Black feminist framework, we describe how participants displayed considerable autonomy by actively forming and withdrawing from sexual relationships with men. However, women described low rates of condom use with main partners and inconsistent use of condoms with more casual sexual partners. This contradiction becomes an important area for sexual health interventions. Women who had sexual relations with only one current mate in the past two years were recruited as a monogamous comparison group.