“…An important, and controversial, issue in genetic toxicology, recently addressed by Ashby andLiegibel (1992, 1993) and Mirsalis (1993), is the dosing regimen, i.e., a single high dose versus repeated low doses. Long-term doses, or even relatively short-term regimens (Mirsalis et aI., 1993a), can induce cell proliferation, and thereby may increase the fixation rate of DNA lesions during mitogenesis.…”