The aims of authorities, university and industrial scientists are outlined. The prime feature remains: How important are the achieved results for estimating the mutagenic risk to humans? The various methods available for the testing of chemical substances for mutagenicity are compared. Their usefulness to estimate the mutagenic risk are considered and the disadvantages and advantages of such methods are discussed. The industrial toxicologist must apply those methods which permit the most accurate conclusions to be made. Further, the toxicologist has to develop new methods which, based on his own experience are more suitable for making more accurate statements. The results of methods carried out on the germ cell of living mammals permit more accurate statements to be made than investigations on isolated cell cultures and somatic cells. Thus, the dominant lethal test on male and female mice and the spermatogenial test on Chinese hamsters are considered suitable methods for estimating the possible dangers to man.