The incidence of helminth parasites in snowshoe hares (Lepus americanus) was studied in 1957–1962 in Michigan's Upper Peninsula. Seventy-five hares were examined for the presence of all helminths, 210 only for certain parasites. Adult tapeworms were present in 5 of 75 (6.7%) hares examined, cysticerci of Taenia pisiformis in 88 of 210 (41.9%), and coenuri of Multiceps sp. in 15 of 179 (8.4%). Nine genera of nematodes were found. Obeliscoides cuniculi occurred most frequently, Nematodirus sp. least frequently. Protostrongylus sp. and Obeliscoides cuniculi appeared to produce pathogenic effects, and Multiceps sp. and Dirofilaria scapiceps may have impaired movement of some hares.