"SUMMARY Male and female CD? (Sprague-Dawley) rats were exposed to commercial hexane vapor at target concentration levels of 0@ 900@ 3000@ or 9000 ppm over two generations. A total uf 25 males and 25 females were evaluated at each exposure level. Following a 10-week pre-breed exposu~e period the FO rats were randomly paired within dose groups for a three (3) week mating period to produce the F1 generation. Exposures continued through mating@ gestation@ parturition and lactation. At weaning on Day 28@ twenty-five (25) Fl wean1ings/sex/group@ were randomly selected to produce the F2 generation. FI pups began exposures to the same concentrations of commercial hexane vapor as their parents the next working day after weaning (at 29-31 days of age). The scheduled eight-week pre-breed exposure period began after the last F1 litter was weaned. After their pre-breed exposure@ Fl animals were paired as described above (for FO parental animals) to produce the F2 generation. All procedures during mating@ gestation and lactation of the F1 parents and F2 weanlings were performed as described above. All Fa and F1 parental animals were necropsied and examined for gross lesions; selected reproductive tissues and tissues from the upper and lower respiratory tract from high dose and control groups were examined histologically as were other tissues with gross lesions. Nonselected Fl and F2 pups were euthanized and discarded at weaning. During the 10 week pre-breed exposure@ FO males and females exhibi':ed no reductions in'body weight. Body weight gain was reduced in FO males at 9000 ppm for one week (Week 6-7) during the pre-breed treatment period; in EO females@ body weight gains were reduced for Week 5-6. Food consumption in FO parental animals was unaffected by treatment. At the FO breed to produce Fl litters@ reproductive parameters were unaffected by treatment. There were no significant reductions in gestational or lactational body weights@ body weight gains or food consumption. The ""no observable effect level"" (NOEL) for general toxicity in adult animals in this study was 3000 ppm; the NOEL for offspring was 3000 ppm@ indicating no increased risk to the offspring in the absence of indications of adul: toxicity. The NOEL for reproductive effects in this study was at least 9000 ppm. The Fl litters at 9000 ppm exhibited reduced body weights per litter on Postnatal Days 14 and 21. Fl pup body weight gains at 9000 ppm were reduced for Lactational Days 7-14 and 14-21. There was no effect of maternal exposure on postnatal deaths (postnatal days 0-28) and there were no apparent treatment-related lesions observed in the necropsy of Fl pups which died during lactation. Treatment-related lesions observed in the histopathologic examination of selected organs from high dose and control FO adults revealed hyaline droplet nephropathy and tubular basophilia in FO males at 9000 ppm. Fl males and females at 9000 ppm began their scheduled pre-breed exposures with reduced body weights. Body weights of Fl males at 9000 ppm remained reduced@ but weight gain was equivalent across groups. Fl females exhibited reduced body weights through Week 2 of exposure and reduced food consumption for Weeks 0-2@ 3-4@ 5-6 and 7-8 of exposure. At the Fl breed to produce F2 litters@ reproductive parameters were unaffected by treatment. Maternal body weights at 9000 ppm were unaffected during the gestational and lactational periods. Gestational food consumption was reduced for Days 0-4@ 4-7@ 0-7 and 7-14 at 9000 ppm. F2 pup body weights per litter were reduced at 9000 ppm for Postnatal Days 7-28. Pup weight gains were also reduced at 9000 ppm for Lactational Days 4-7@ 7-14 and 14-21. Perinatal deaths and lactational survival were unaffected by treatment. There were no exposure-related lesions observed in the necropsy of F2 pups which died during lactation. Treatment-related lesions observed in the histopathologic examination of selected organs from high dose and control Fl adults indicated hyaline droplet nephropathy and tubular basophilia in Fl males at 9000 ppm. There were no apparently exposure-related deaths of adult animals on study. In summary@ exposure of CD? rats to commercial hexane vapor for two generations resulted in parental toxicity at the target dosage level of 9000 ppm; perinatal toxicity was concomitant with parental toxicity@ being well-defined at 9000 ppm. There were no treatment-related reproductive effects observed in this study. The ""no observable effect level"" (NOEL) for general toxicity in adult animals in this study was 3000 ppm; the NOEL for offspring was 3000 ppm@ indicating no increased risk to the offspring in the absence of indications of adul: toxicity. The NOEL for reproductive effects in this study was at least 9000 ppm."