A suspension of C particles was injected in the amniotic sacs of 431 rat fetuses 1-2 days prepartum. Approx. 75% were still-born and only 15% were living 24 hrs. after birth. In contrast, 58% of a group of 162 fetuses in which normal saline was injected into the amniotic sac under similar conditions were living 24 hrs. after birth. Over 90% of the still-born animals showed C particles in the lungs when autopsied. Since some animals did survive 24 hrs. after birth and showed no C in the lungs, it cannot be contended that aspiration of amniotic fluid is a normal physiological process. The high incidence of still-births in both series leads to the conclusion that the excessive respiratory stimulation resulting from the fetal anoxia and hypercapnia attendant on the anesthetic and operative procedure caused the animals to inspire amniotic fluid.