The trifunctional alkylating mutagen Trenimon interferes with the genetic material of a variety of organisms and test systems with respect to the induction of point and chromosomal mutations, sister-chromatid exchanges, recombination phenomena and phage induction. Beneath these mutagenic effects several biochemical and cell physiological aspects have been investigated. In this review we discuss chemical and cell physiological effects of Trenimon, aspects of cancer therapy with Trenimon and genetic effects induced by Trenimon. The available data on mutagenic effects of Trenimon are presented according to organisms or test systems. A short discussion on a possible genetic load by therapy with Trenimon in man concludes this review. DNA damage, especially the induction of cross-linkings, seems to represent the common reason for most of the described effects of Trenimon on cells and organisms.