Cytotoxic chemotherapy is routinely used in the treatment of cancer, and has been an important factor in increasing 5-year survival rates for some types of this disease. A range of drugs are currently available, with differing modes of action. As well as causing some direct toxic effects, most if not all of these drugs are both mutagenic and carcinogenic. Although comparative information on these properties is generally available for anticancer drugs which alkylate DNA, it has been less readily accessible for other drug classes. This special issue contains seven reviews on the mutagenic properties of the major classes of cytotoxic drugs in clinical use, as well as one on a class of drugs that is under development. Some carcinogenicity data are also summarised, where available. Additionally, there are four more general papers, including one on the use of genetic activity profiles for comparing mutagenicity of the drugs, two on germ-cell effects, and one on biomonitoring for exposure to genotoxic anticancer drugs.