This document represents the views of ICPFMC and is published by IPCS in an attempt to stimulate scientific discussion, as well as to provide guidance on the use of genotoxicity tests in chemical safety programmes. Although short-term tests to screen for mutagenicity and carcinogenicity are useful, they have their difficulties and limitations. The present document reflects a widely-used approach that may be regarded as good contemporary practice. It is designed to explain the types of test that are commonly employed and the meaning that the results of such tests may have in the assessment of possible human hazard, as far as is possible with current scientific knowledge.