Corallobothrium fimbriatus, a tapeworm, was described from the intestines of catfishes (Ameiurus melas (Black Bullhead) and Ictalurus punctatus (Channel Catfish) from Lake Pepin on the upper Mississippi River, and from Sturgeon Bay, Lake Michigan. Corallobothrium fimbriatum infects many species of catfishes of the family Ictaluridae, and its native range extends from Quebec to Mexico, including the Great Lakes, Mississippi basin, and other Gulf of Mexico drainages. This tapeworm was introduced to the Colorado River system, Arizona in Channel Catfish (Ictalurus punctatus), and to the Sacramento-San Joaquin Delta, where it was collected in introduced White Catfish (Ameiurus catus), Black Bullhead (A. melas), and Channel Catfish.