A procedure has been developed for purification of the tripartite anthrax-toxin components. This involves sequential high-performance anion-exchange, gel-filtration and hydrophobic-interaction chromatography. From an initial culture volume of 15 litres, typical yields of 8 mg of protective antigen, 13 mg of lethal factor and 7 mg of oedema factor are produced to higher degrees of purity than have previously been achieved by conventional chromatographic techniques.