The developmental toxicity of diethylene-glycol-monomethyl-ether (111773) (DEGME) was studied in rats. Pregnant Sprague-Dawley-rats were administered 1000, 1495, 2235, 3345, or 5175mg/kg DEGME orally on gestational days 7 to 16 in a preliminary range finding study. Surviving dams were killed on gestational day 21 and the uteri were removed. Two of nine rats given 5175mg/kg died. All rats in this group had significantly reduced body weight gain and feed consumption. Body weight gain was significantly reduced in 3345mg/kg dams, but no deaths occurred. All litters in the 5175mg/kg group and six of nine litters in the 3345mg/kg were completely resorbed. Dose related increases in the incidence of fetal visceral and skeletal malformations were seen in the other groups. Pregnant rats were administered 720 or 2165mg/kg DEGME on gestational days 9 to 16. The 2165mg/kg dose significantly decreased maternal feed consumption and body weight gain. Fetal weight and litter size were significantly decreased by 2165mg/kg DEGME. The 720mg/kg dose did not induce maternal toxicity or significantly affect fetal weight or litter size. DEGME induced a dose related increase in the incidence of skeletal malformations consisting primarily of rudimentary developed cervical ribs, delayed ossification, bilateral wavy ribs, and cardiovascular malformations. When all malformations were combined, the percentage of control litters and 720 and 2165mg/kg litters having at least one malformation was 22.7, 52.4, and 90.5%, respectively. The authors conclude that DEGME is teratogenic, embryotoxic, and fetotoxic to rats at doses that are not maternally toxic.