Abstract: The present invention relates to the use of toxoids prepared using a-dicarbonyl toxoiding reagents such as glyoxal, butanedione and phenylglyoxal. The toxoids may be prepared with low concentrations of toxoiding reagent and in short periods of time, often in as few as 24 hours, making the toxoiding reagents particularly advantageous when compared with traditional formaldehyde toxoiding. Toxoids prepared using dicarbonyl reagents such as phenylglyoxal are described and claimed as are pharmaceutical and vaccine compositions comprising the toxoids, methods of treatment using such compositions and antibodies generated by immunisation with the toxoid and methods of treatment using the antibodies so prepared or fragments of such antibodies.