8 term fetal pigs (110-112 days gestation) and one 97-day fetus were asphyxiated in utero by occlusion of the umbilical cord. Mean times to last gasp and last heart beat were 5.1 and 22.4 for term and 5.4 and 30.4 min for the 97-day fetus. Cord occlusion was followed by profound bradycardia and an increase in blood pressure which was maintained until gasping ceased. Profound acidemia, hypercapnia and hyperlactacidemia developed in all animals and values following asphyxiation were comparable with those seen in stillborn piglets. Liver and cardiac glycogen levels were lower in asphyxiated fetuses than in littermates but muscle glycogen levels were similar in both groups.