IARC and the US National Institutes of Health have now been joined by the French Ministry of the Environment for the development of this programme on the establishment and validation of methods which can be used for the decontamination of wastes contaminated by chemical carcinogens and the treatment of spillages with such compounds. Eight volumes have been published dealing with aflatoxins, nitrosamines, polycyclic aromatic hydrocarbons, hydrazines, nitrosamides, haloethers, aromatic amines and a series of antineoplastic agents (IARC Scientific Publications Nos 37,43,49,54,55,61,64, and 73). In this volume, the ninth of the series, methods of degradation are presented for four commonly investigated mycotoxins: ochratoxin A, citrinin, patulin and sterigmatocystin. In view of new findings, a re-investigation has also been performed for aflatoxins and these compounds have been tested in one of the methods. The five methods presented are described in an ISO style format. They can be applied to various waste categories and three of them to spillage treatment.