Timed pregnant Fischer 344 rats and New Zealand White rabbits were exposed to vapor from ethylene glycol monohexyl ether (EGHE, CAS No. 112-25-4) for 6 hr/day on gestational days (gd) 6 through gd 15 (rats) or gd 6 through gd 18 (rabbits) at analytically measured concentrations (as means +/- SD) of 20.8 +/- 0.90, 41.1 +/- 1.77, or 79.2 +/- 10.8 ppm; control animals were exposed to air alone. Monitors for maternal toxicity were body weight, food and water consumption, clinical signs, and hematology. At sacrifice (gd 21 rats, gd 29 rabbits) maternal weight, liver weight, and gravid uterine weight were measured. Gestational parameters monitored were numbers of corpora lutea, preimplantation losses, viable implants, early and late resorptions, and dead fetuses. Live fetuses were sexed, weighed, and examined for external, visceral, and skeletal malformations and variations. Rabbit maternal toxicity occurred at 79.2 ppm as transient weight gain reduction during the exposure period. For maternal rats at 79.2 ppm, there were transient decrease in body weight and body weight gain during exposure, reduced food consumption, increased water consumption, and excess lacrimation. At 41.1 ppm, maternal body weight gain was reduced during the exposure period only. There were no treatment-related effects with respect to hematology, necropsy, or gestational parameters and no significant change in the incidence of malformations or variations (expressed as total, individual, external, visceral, or skeletal). Thus, exposure of rats and rabbits to EGHE vapor during the period of organogenesis produced maternal toxicity at near-saturation vapor concentrations (79.2 ppm), but no evidence for developmental toxicity or teratogenicity. The no-effect vapor concentrations for maternal toxicity were 41.1 ppm for rabbits and 20.8 ppm for rats.