Mammalian in vivo bone marrow chromosomal aberration testing is particularly important for assessing genotoxicity, as in vivo metabolism, pharmacokinetics, and DNA repair processes are active and have been found to be important in genotoxic responses, although they may differ between species. The mammalian in vivo chromosomal aberration test is used to detect structural chromosome aberrations caused by test chemicals in bone marrow cells of animals, usually rodents.