Technical Abstract: Romet ( a blend of ormetoprim and sulfadimethoxine) is a type A medicated article for the manufacture of medicated feed in the catfish industry. Recently, the commercial manufacture of ormetoprim-sulfadimethoxine susceptibility discs was discontinued. Ormetoprim-sulfadimethoxine discs were prepared at the Mississippi State University College of Veterinary Medicine Aquatic Diagnostic Laboratory according to Clinical and Laboratory Standards Institute guidelines. The performance of the laboratory-prepared discs was compared with that of commercially prepared discs in disc diffusion assays with 23 field isolates of Edwardsiella ictaluri. The a priori limits of agreement for the laboratory-prepared ormetoprim-sulfadimethoxine discs were + 5mm of the zones for the commercial discs. The resulting zones of inhibition ranged from 33 to 50 mm and from 35 to 52 mm for the laboratory-prepared and commercially prepared discs respectively. The data comparing the two sets of discs were analyzed to determine the level of agreement. The analysis demonstrated that the laboratory-prepared discs produced slightly smaller zone of inhibition than the commercially prepared ones. The observed limits of agreement were within the a priori established limits of agreement, indicating that the laboratory-prepared ormetoprim-sulfadimethoxine discs were acceptable replacements for the commercially prepared discs.