The teratologic effects of inhaled methanol (67561) and ethanol (64175) were evaluated in rats. Bred female Sprague-Dawley-rats were exposed on gestation days 1 to 19 to 7 hours per day exposures of 0 to 20,000 parts per million (ppm) methanol or ethanol. Females were killed on gestation day 20 and effects on corpora lutea, resorptions, live fetuses, and fetal malformations were determined. Methanol was toxic to dams only at the highest concentration, 20,000ppm producing a slightly unsteady gait. Ethanol was severely toxic, the 20,000ppm group being completely narcotized at the end of exposure. Dams exposed to 16,000 and 10,000ppm ethanol appeared hyperactive. Methanol exposure did not affect the numbers of corpora lutea or implantations, or the percentage of dead or resorbed fetuses. However, 10,000 and 20,000ppm methanol depressed fetal weights in a dose dependent fashion. Dose related increases in fetal malformations were also apparent after methanol exposure. Nine fetuses showed external malformations in the 20,000ppm group; 14 of 15 litters had one or more skeletal malformations and visceral malformations were seen in 66 percent. Twenty two percent of fetuses receiving 10,000ppm methanol and 69 percent of those exposed to 20,000ppm showed skeletal variants, compared to 12 percent in controls. Ethanol did not significantly affect fetal weights of female pups, but it did depress the weight of male pups in both the 16,000 and 20,000ppm ethanol exposure groups. There was no significant difference in the incidence of skeletal or visceral malformations or of visceral or skeletal variations, although the 20,000ppm group had seven litters with abnormal fetuses as opposed to a high of four litters in one control group. The authors conclude that methanol is teratogenic at high concentrations by inhalation exposure, with 5,000ppm being the no effect concentration in this test system. Further, 10,000 to 20,000ppm ethanol administered via inhalation is not teratogenic in rats.