Groups of forty Sprague-Dawley rats, evenly divided by sex, were exposed to vapors of MCTR-242-79 at target concentrations of 10, 30, 100 and 300 ppm for 6 hours per day, 5 days per week, for up to four weeks and then left untreated for a further four weeks. Up to five male and five female rats from each group (unless precluded or reduced by mortality) were sacrificed 2, 4 and 6 weeks after commencement of exposure; the remaining survivors were sacrificed after eight weeks.