AbstractThe effect of L‐glutamic acid on the embryolethal and terato‐genic action of trypan blue was investigated in Wistar albino rats. L‐glutamic acid was either incorporated into the diet, from gestation day 2 to day 20, or suspended in sesame oil and administered by gavage, from gestation day 6 to day 10. The day of finding sperm in the vaginal smear was designated day 0 of pregnancy. A teratogenic dose of trypan blue was injected at day 8 of pregnancy, either intraperitoneally (14 mg/kg maternal body weight) or subcutaneously (160 mg/kg). The amount of glutamic acid consumed, after the injection of trypan blue, ranged from 600 to 1,500 mg/rat/day. Pregnancy was terminated at day 20, and the fetuses were recovered and examined. Glutamic acid failed consistently to protect the rat embryo against the lethal and teratogenic action of trypan blue. These results are in contrast to those obtained in mice. The administration of sesame oil alone was found to cause embryonic death, but not malforma