Perennial pepperweed (Lepidium latifolium L.) is an aggressive perennial forb that is infesting much of western North America. Grazing may provide an alternative to chemical and mechanical control of perennial pepperweed. However, if livestock are used in control efforts, they may spread weeds by depositing viable seeds in fecal pats in uninfested areas. This study consisted of 2 experiments using fistulated steers to estimate the effect of ruminant digestion on germination of perennial pepperweed seeds. In Experiment 1, we tested the hypothesis that ruminal incubation (for 0, 48, and 96 hours) affects perennial pepperweed germination. In Experiment 2, we tested the hypothesis that type of incubation (no incubation, water only, or total digestive tract) affects perennial pepperweed germination. In Experiment 1, germination was 17 and 15 times greater for the 48- and 96-hour incubation treatments compared to the control, respectively. In Experiment 2, germination was 23 and 19 times greater for the water and total tract incubation treatments compared to the control, respectively. Effects were attributed to a combination of seed hydration and seed coat scarification. Results from this study suggest that grazing should occur prior to seed set or that livestock which have grazed perennial pepperweed bearing viable seed should be quarantined before being moved to uninfested areas. These results also suggest that control of perennial pepperweed is especially important where moving water may transport seeds off site.