Researchers in the evolutionary sciences have long understood men's desire to mate with a variety of women. Because men's obligatory investment in offspring production is relatively small, men can directly increase their number of descendants by mating with multiple partners. Relatively less is known, however, about the conditions that favor sexual variety seeking in women. Drawing on insights from evolutionary biology and behavioral ecology, we examined the relationship between the perceived pathogen load in an environment and women's desire for sexual variety. Across 5 experiments, we primed women with cues indicating that the rate of disease is increasing in their environment. We then measured their desire for novel sexual and dating partners. Results revealed that women with a history of vulnerability to illness respond to these cues by desiring a greater number of novel partners. This shift was not found in men and did not predict variety seeking in a nonsexual domain. In addition to providing evidence of a novel conceptual link between the pathogen load and patterns of human mating behavior, this research also provides new insights into women's mating psychology and the conditions that favor sexual variety seeking in the greater investing sex.