A strain of Clostridium botulinum Type E in a beef heart infusion – peptone broth yields moderate amounts of toxin when grown at 30 °C. but fails to produce toxin at 37°. When grown in a cellophane sac suspended in a similar medium, at 30 °C, there is a 5- to 10-fold increase in the yield of toxin. Toxoid has been prepared from the high potency cellophane produced toxin by clarification with charcoal, Mandler filtration, and detoxification with 0.3% formalin at 30 °C. for 20 days. Three doses of the fluid toxoid protects mice against 500 M.L.D. of homologous toxin. One dose of the same toxoid adsorbed on alum affords the same level of protection as three doses of the fluid toxoid. Mixing Type E toxoid with equal amounts of Types A and B in vitro augments the antigenic action of the Type E toxoid.