Abstract: The present invention relates to detoxified immunogenic derivatives of Clostridium perfringens &bgr;-toxin or an immunogenic fragment thereof that have as a characteristic that they carry a mutation in the &bgr;-toxin amino acid sequence, not found in the wild-type &bgr;-toxin amino acid sequence. The invention also relates to genes encoding such &bgr;-toxins, as well as to expression systems expressing such &bgr;-toxins. Moreover, the invention relates to bacterial expression systems expressing a native &bgr;-toxin. Finally, the invention relates to vaccines based upon detoxified immunogenic derivatives of Clostridium perfringens &bgr;-toxin, and methods for the preparation of such vaccines.