Sixty-nine strains of Clostridium perfringens of different toxigenic types were investigated for enterotoxin production. Enterotoxin was definitively detected only in strains of types A and C. This is the first report where enterotoxin production has been demonstrated in a toxigenic type other than type A. The exterotoxin-positive type C strains were isolated from cases of enteritis necroticans ("pig bel+) in New Guinea. The major enterotoxin from type C showed a reaction of complete identity with enterotoxin from type A in immunodiffusion using anti-enterotoxin serum prepared against the latter; it induced erythema when injected intradermally into depilated guinea pigs and caused fluid accumulation in the rabbit ileal loop. The results indicate that the major enterotoxin from type C was serologically and biologically similar to enterotoxin from type A. In some C was serologically and biologically similar to enterotoxin from type A. In some type C strains, an enterotoxin was detected that showed a reaction of partial serological identity. Spore coat proteins were extracted from 14-strains by alkaline dithiothreitol, and the extracts were assayed for enterotoxin-like spore protein. Enterotoxin could be extracted from type A and type C spores, and all positive strains showed a reaction of complete identity in immunodiffusion with enterotoxin obtained from cell extracts of type A. Disc immunoelectrophoresis demonstrated that two distinct components that reacted serologically with anti-enterotoxin serum were present in both the cell extract and in extracted spore protein from one type C strain. These distinct components differed in molecular weight.