Results obtained in our laboratory have shown that certain strains of Clostridium perfringens produce a readily detectable enterotoxin capable of producing diarrhea, the major symptom of perfringens food poisoning, in experimental animals and in humans. Although we have purified the enterotoxin and determined some of its biochemical properties, anomalous behavior of the toxin has been observed in certain chromatographic, electrophoretic and analytical ultracentrifugation experiments. The proposed research will permit continuation of our investigations to biochemically and serologically characterize the toxin. Enzymatic and some chemical modification of the purified toxin will be made to investigate structure-biological activity relationships. Large quantities of purified enterotoxin and specific antiserum will be prepared to meet continuing requests for these materials by other researchers. Affinity chromatography will be investigated as a purification technique for the toxin. In addition, a recently discovered paracrystalline inclusion, produced only by sporulating, enterotoxin positive strains, will be isolated and purified. Possible biochemical, serological and biological activity homology between the inclusion and enterotoxin protein will be determined.