The carbamate insecticides benfuracarb, carbosulfan and furathiocarb were investigated in the mouse bone marrow micronucleus assay to establish whether they show cytogenetic activity in vivo. Two doses of each substance were administered intraperitoneally to NMRI mice. All of the three substances led to a positive micronucleus response in polychromatic erythrocytes of the bone marrow at different expression times. While furathiocarb and carbosulfan showed similar patterns of the time-dependence of the micronucleus formation with maximum values after 72 h, benfuracarb exhibited a different behaviour with the maximum increase taking place within 24 h after substance application. In furathiocarb-treated animals the ratio of normochromatic to polychromatic erythrocytes showed a dose and time depending increase with the highest value obtained after 72 h in animals treated with the upper dose. The two yeast test systems Saccharomyces cerevisiae strains D7 and D61.M were applied in order to evaluate the genetic endpoints gene mutation, gene conversion and aneuploidy induction. None of the three insecticides had an influence on the frequencies of gene conversion and reverse mutation in the yeast S. cerevisiae D7 when tested with and without metabolic activation. In strain D61.M however benfuracarb and furathiocarb led to an increase of chromosome loss in the presence of the S9 metabolizing system.