To determine the potential developmental toxicity of ethylene glycol monopropyl ether (EGPE), groups of pregnant New Zealand white rabbits were exposed to target concentrations of 0, 125, 250, or 500 ppm EGPE vapors for 6 hr a day on Days 6-18 of gestation. Maternal effects included a slight reduction in feed consumption during the first week of treatment at the 250- and 500-ppm exposure levels and slightly reduced body weight gain at the 500-ppm level compared to those of the controls, but the differences were not statistically significant. One doe exposed to 500 ppm had red-colored urine during the 24-hr period following the second exposure. Hematologic determinations, absolute and relative organ weights, and observations at necropsy revealed no treatment-related maternal effects. Reproductive indices, i.e., pregnancy rate, number of corpora lutea, implantation sites, viable fetuses, early and late resorptions, fetal body weights, fetal sex ratio, and the gravid uterine and corrected body weights, were not affected by exposures to EGPE. The occurrences of external and internal soft tissue malformations and variations and the incidences of skeletal malformations in the EGPE-exposed groups were not significantly different from those in the control group. Common skeletal variations, in many instances, were seen less frequently in EGPE-exposed fetuses than in control fetuses. In those cases where the incidence of fetuses with a skeletal variation was greater for EGPE-exposed fetuses than that for control fetuses, the number of litters involved was not significantly different from that of the control group. Thus, EGPE vapor concentrations as high as 500 ppm did not produce teratogenicity or other developmental toxicity in the rabbit conceptus.