Botulism anatoxin, accurately prepared, is absolutely harmless to man. A multiple subcutaneous immunization of 40 testees with anatoxin caused neither general, nor local symptoms. The immunization with anatoxin developed immunity to botulism in man. The effectiveness of immunization depends on a dose of administered antitoxin. The resumption of immunization (even a single administration) after one year resulted in a distinct increase of immunity to botulism.