Seed predation has the potential to strongly reduce seed production and thereby act as a selective force on the evolution of flowering traits and other defenses against herbivory. We characterized levels of predispersal seed predation on Hibiscus moscheutos (Malvaceae) during 2001 and 2002 at four sites in Ohio and Maryland, USA. The seed predators were a weevil, Conotrachelus fissinguis (Coleoptera, Curculionidae) and a bruchid beetle, Althaeus hibisci (Coleoptera, Bruchidae). The weevil occurred at three of the four sites and damaged 24% to 94% of fruits in these populations. The bruchid occurred at all four sites, where it destroyed 4% to 27% of the seeds. Seed predation varied between years and among sites for both predators and year-by-site interactions were common. Variation in predation levels indicates that seed predators did not influence this species uniformly, but they were often abundant and sometimes destroyed nearly all of the seeds produced. At one of the Ohio sites, we assessed levels of seed predation at 5-d intervals during the 2001 flowering season. At this population, bruchid damage was greatest for seeds produced by flowers that opened in late July, when flowers were scarce, whereas weevil damage was greatest in mid-August and coincided with peak flowering. The timing and greater extent of weevil damage suggest that they may have a greater effect on plant fitness than bruchids.