The reproductive and developmental toxicology of styrene-oxide (96093) (SO) was studied in female rats and rabbits exposed to SO by inhalation. Three groups of 5 week old female Wistar-rats were exposed to SO vapor at 0, 100, or 300 parts per million (ppm) for 7 hours/day, 5 days/week for 3 weeks prior to mating. Exposure to 300ppm was rapidly lethal and this group was eliminated from further study. The rats exposed to 0 and 100ppm SO were mated and then randomly divided into two subgroups for gestational exposure to 0 or 100ppm (7 hours/day, 7 days/week) SO continuing through 18 days of gestation (dg). Sexually mature, virgin, female New-Zealand-White- rabbits were artificially inseminated and exposed to 0, 15, or 50ppm SO for 7 hours/day through 24dg. Rats were sacrificed at 20dg and rabbits at 30dg. In both rats and rabbits, exposure to SO resulted in a statistically significant increase in mortality, and statistically significant reductions in mean body weight and mean food consumption. The percentage of rats that were pregnant was significantly reduced in the groups exposed after mating; SO exposure had little effect on other measures of reproductive success. In rabbits, exposure did not affect the percentage of pregnant rabbits, but did significantly increase the fraction of litters with resorptions. Incidence of resorptions increased from the 15 and 50ppm groups, respectively. Gestational exposure resulted in reduced fetal weights and crown/rump lengths in rats and rabbits, and increased the incidence of ossification defects of the sternebrae and occipital bones in rats. The authors conclude that SO may be regarded as producing reproductive and developmental toxicity at the levels studied, although it has not been established whether these are direct effects or are the result of maternal toxicity.