The main objective of the pharmaceutical industry is health protection. Drugs not intended for use in life-threatening diseases should be free from toxic effects, but every natural or man-made chemical has potential toxicity depending on the exposure dose. The pharmaceutical industry considers genetic toxicology as a part of overall safety evaluation. No single genetic toxicity test is satisfactory; a battery of test is necessary to cover the whole spectrum of genetic events. Numerous tier approaches have been proposed for mutagenicity testing but from the toxicological viewpoint a phylogenic testing model seems more appropriate than a sequential step model. Evaluation of the mutagenic potential of drugs should rely on in vivo animal models, although for screening purposes and to promote understanding of the mutagenic action, in vitro tests using different systems can be used. Rejection solely on the basis of in vitro tests can lead to the unnecessary loss of a valuable drug. More inexpensive and relatively short tests on non-mammalian and mammalian cells are needed for studying structure-mutagenic activity relationships. For extrapolating to man and in the framework of clinical studies, it might be worthwhile to focus more time on developing inexpensive and simple tests using models directly relevant to man (e.g. human body fluids).