The acid-base balance and the concentrations of lactate, pyruvate, citrate, alphaketoglutarate and total acetone bodies have been studied in human amniotic fluid and in cord blood. Lactate and citrate concentrations are elevated in amniotic fluid, the other acids being present in a concentration similar to that in blood. Lactate accounts for only a part of the total metabolic acidosis in cord blood. The concentration of the other organic acids studied does not explain this difference. The lactate and pyruvate concentrations are significantly correlated with the degree of metabolic acidosis in cord blood expressed as negative base excess, the other acids showing no correlation with the degree of acidosis and asphyxia.