IARC and the NIH were joined by the French Ministry of the Environment in the development of a program to establish and validate methods 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 can be applied to various waste categories and three of them to spillage treatment. Chemical and biological information concerning these compounds is also presented in an appendix to these methods.