Term monkey fetus 1620 sustained 50 min of rapidly developing severe asphyxia which began immediately after its in utero version. The arterial blood pO2 decreased from a normal value of 34 to 11-12 mm Hg while the blood pH fell from 7.35 to 6.70. During this asphyxia, hemoglobin-oxygen saturations below 5% were recorded. The complete collapse of the umbilical circulation several minutes prior to the reoxygenation of the fetus added an episode of total asphyxia. With reoxygenation following delivery, fetal cardiovascular performance improved rapidly though over an hour was required for recovery from the severe acidosis. The animal prospered but was found moribund on the 13th postnatal day due to dehydration. Brain examination after euthanasia revealed severe paracentral cortical and basal ganglia damage. Damage also appeared symmetrically in nuclei in the lower brain stem and in thalamus. These three zones of injury are attributed to the partial, the partial combined with the total, and the total asphyxia, respectively. The present case makes clear that compression of the umbilical cord may cause damage of a variety of types depending on the severity and duration of the asphyxia induced. It also demonstrates the possibility of recovery from a systemic acidosis where the pH values have fallen to levels below 6.70 for up to an hour.