Recent events have increased the interest in the treatment of clostridial infections. During World War II a considerable amount of information was accumulated on the efficacy of sulfonamides (McKee et al, 1943; Hac and Hubert, 1944; Hac, 1944a; Langley and Winkelstein, 1945; Ryan et al, 1946) and of penicillin (McKee et al, 1943; Hac, 1944b; Macfarlane, 1945) in the treatment of experimental and clinical gas gangrene. With the advent of the newer antibiotics (Duggar, 1948; Ehrlich et al, 1947; Hobby et al, 1950) it was felt desirable to compare them with penicillin, which had shown encouraging results in earlier work. A number of investigators have evaluated the effectiveness of aureomycin against experimental Clostridium perfringens infections (Altemeier et al, 1950; Sandusky 1950), but only one paper dealing with the experimental evaluation of aureomycin, terramycin and penicillin against Clostridium septicum and Clostridium tetani infections has come to our attention (Bliss et al, 1950).