Historically, interest in the infectious agents of prairie grouse (Tympanuchus spp.) (PG) mirrored trends in how North American wildlife scientists perceived host–parasite interactions. Increased ecological interest in host–parasite interactions since the 1980s led to increased awareness of PG–parasite interactions beginning in the 1990s Prairie grouse are hosts to parasitic arthropods (e.g., lice, mites, ticks) and helminths (e.g., nematodes, cestodes, trematodes), as well as microparasites such as protozoa, bacteria, fungi, and viruses. Although many of these infectious agents cause disease individual PG, few data address their potential influence on host population dynamics Based on existing data on the parasites of PG, studies of other grouse species, and the oretical perspectives, the macroparasites Dispharynx nasuta and Trichostrongylus cramae; the microparasites Eimeria dispersa, E. angusta, Leucocytozoon bonasae, and Plasmodium pedioecetii; and the infectious bronchitis and reticuloendotheliosis viruses exhibit characteristics that suggest they have the potential to regulate PG populations. Infectious agents such as Histomonas meleagridis, Pasteurella multocida, dispersa, E. angusta, and other microparasites that cause high mortality across a broad range of galliform hosts have the potential to extirpate small, isolated PG popu lations. Nonparasitic diseases caused by mycotoxins, pesticides, and other toxic com pounds also have the potential to influence population dynamics. Because there appears to be a behavioral component to PG population extinction, the fact that para sites might influence breeding behavior also requires further evaluation. Although it difficult to establish whether parasites regulate their host populations, research models such as that associated with T. tenuis in red grouse (Lagopus lagopus scoticus) available for reference. These approaches could be used to determine whether relevant macro- and microparasites influence the dynamics of declining or at-risk PG pop ulations. Natural-resource policy-makers must become aware that macro- and microparasites of PG are not something they can safely ignore and should fund research designed to determine whether parasites regulate or have the potential to extirpate PG populations while there is still time for management intervention.