||Despite widespread evidence for the benefits of polyandry, there are costs associated with each mating for females, and for many species, it is unknown whether the costs of extra matings outweigh the benefits. In the seed beetle Callosobruchus maculatus (Coleoptera: Chrysomelidae: Bruchinae), costs might come from male harassment during mating attempts or from injuries that females sustain during copulation. Benefits of mating might come from nutrients or water transferred in the ejaculate. If mating is costly overall, male presence (sexual harassment) and multiple mating in C. maculatus is expected to reduce female fitness. Females were housed with differing numbers of males (1–4) and differing opportunities for copulation. When females were both harassed by and could remate with more than one male, they had lower lifetime reproductive rates and reduced life span relative to monandrous females. These results indicate that when females are continually exposed to multiple males, the direct benefits of multiple mating do not compensate for the costs.