Author Institution: Department of Zoology, The Ohio State UniversityA total of 166 Brown-headed Cowbirds was examined for the occurrence of helminth parasites. Of these, 116 were collected on the campus of The Ohio State University, Franklin County, Ohio, from January 1964 through February 1965. The remainder of the birds were collected on South Bass Island, Ottawa County, Ohio, from July 1969 through July 1970. Twenty species of helminth parasites are recorded from these birds. Sixteen of these helminth species are new host records: the trematodes Conspicuum icteridorum, Lutztrema sp., Prosthogonimus macrorchis, Tanaisia zarudnyi, and Zonorchis alveyi; the cestode Orthoskrjabinia rostellata; the nematodes Capillaria caudinflata, C. ovopunctatum, C. tridens, Chandlerella quiscali, Diplotriaena bargusinica, Microtetrameres sp., Splendidofilaria algonquinensis, Syngamus trachea, and Tetrameres americana; and the acanthocephalan Plagiorhynchus formosus
