In 2002, New Jersey Division of Fish and Wildlife biologists conducted an aquatic assessment in a section of the Cohansey River in Cumberland County. Three of seven tadpole madtoms Noturus gyrinus collected were observed to have an ulcerative lesion on the head between the eyes. Gram-negative, oxidase-negative rods were isolated from the head kidneys of two of the madtoms and from the cranial ulcer of the third madtom. Four different identification methods--API-20E, whole-cell fatty acid methyl esters (FAME), BIOLOG, and enterobacterial repetitive intergenic consensus (ERIC) sequences-ascribed the isolates to the species Edwardsiella ictaluri. A phenotypic comparison using FAME and BIOLOG data revealed that E. ictaluri isolates from wild madtoms shared a high degree of similarity to E. ictaluri isolates from cultured channel catfish with enteric septicemia of catfish (ESC) from southeastern states. However, fingerprinting by amplified fragment length polymorphisms (AFLP) demonstrated that the three madtom isolates were genetically different from the other E. ictaluri isolates. Koch's postulates were fulfilled by using the tadpole madtom E. ictaluri isolate in juvenile channel catfish. Sixty percent mortality was achieved in intraperitoneal injection of catfish with the isolate (1 x 10 super(4) colony-forming units/ fish), produced 60% mortality. The results indicate that the ictalurid tadpole madtom is susceptible to ESC by natural infection. This is the first report of a bacterial disease affecting tadpole madtoms.