This paper examines the shifting nature of contemporary epidemiological classifications in the HIV/AIDS epidemic. It first looks at assumptions that guide a discourse of vulnerability and circulate around risk categories. It then examines the underlying emphasis in public health on the popular frame of "vulnerable women" who acquire HIV through heterosexual transmission. Drawing on work on gender, sexuality, and intersectionality, the paper asks why a discourse of vulnerability is infused into discussions of heterosexually-active women's HIV risks but not those pertaining to heterosexually-active men's. The paper then moves to current surveillance categories that are hierarchically and differentially applied to women's and men's risks in the HIV epidemic. Here, the focus is on the way in which contemporary classifications allow for the emergence of the vulnerable heterosexually-active woman while simultaneously constituting lack of fathomability concerning bisexual and lesbian transmission risk. Lastly, theories of intersectionality, are used to examine current research on woman-to-woman transmission, and to suggest future more productive options.