Tetrahydrofuran (CAS No. 109-99-9) was evaluated for developmental toxicity in groups of 14, 7, 6, 7, and 7 pregnant CD rats, exposed to 0, 200, 500, 2500 or 5000 ppm respectively for 6 hours/day from days 6 through 15 of gestation. Dams at 5000 ppm did not respond to a sound stimulus, had poor muscle tone and a staggered gait during exposure. Maternal body weight gain from days 1-21 of gestation in the high dose group was less than controls, but the difference was not statistically significant. At 5000 ppm the mean fetal body weight was significantly less than controls and petechial hemorrhage was significantly different from controls. No evidence of teratogenic potential was demonstrated. Embryotoxicity occurred at 5000 ppm, which was the concentration toxic to dams. No other differences in terms of implants, fetal malformations (external, visceral, skeletal), or variations were reported as significantly different from controls.