Abstract: A method is provided for the purification of Clostridium difficile Toxin A antigen comprising reacting impure Toxin A with immobilized mono-specific polyclonal antibodies. The polyclonal antibodies are coupled to a hydrazide group containing matrix such as hydrazide activated agarose gel. The immobilized antibody is specific for Toxin A and will greatly purify Toxin A from a Toxin A containing solution. Antibodies raised to Toxin A purified according to the method are of higher activity than antibodies produced from prior art purified Toxin A.