The effectiveness of halogens or halogen-containing compounds in destroying purified and partially purified Clostridium botulinum toxins, under varying conditions of pH, temperature, and length of exposure, has been evaluated. The detoxifying substances studied were free chlorine, chloramine, Globaline, and chlorine dioxide. Free available chlorine in concentrations sufficient to provide residuals of one mg/1 will destroy at least 99.9 percent of all five types of botulinum toxin in five minutes or less. Chlorine dioxide is somewhat more effective than free available chlorine in destroying the toxin most resistant to chlorine. The type E toxin is the most resistant of the five types to destruction by chlorine. (Modified author abstract)