The purpose of this feminist grounded theory study was to understand the meaning and experience of postmenopausal women's sexual desire. Data collection from 22 postmenopausal women who were ongoing participants of the TREMIN Research Program on Women's Health occurred via audiotaped, telephone-based, semistructured interviews. Women's descriptions of their sexual needs and desires led to the discovery of the core category, negotiating sexual agency, which refers to women's ability to act on behalf of their sexual needs, desires, and wishes. Women negotiated their sexual agency within three main domains (or axial codes): their own sexual self, their partners, and the medical system. An important finding was women's internalization of sociocultural assumptions that privilege their male partners' sexual needs over their own. The findings of this study, especially the contexts in which women negotiate their sexual agency, are important for women, women's health care providers, and women's life partners to understand.