A full term neonate in which by accident a metabolic alkalosis was found, is described. The origin of the metabolic alkalosis was excessive vomiting by the mother during the days prior to delivery. The simplified form of the Henderson Hasselbalch equation is used to describe the factors responsible for the generation of metabolic alkalosis. Consequences for the neonate are mentioned, especially the vasoconstriction of the cerebral vessels is discussed. Treatment should be rehydration and administration of sodium-chloride.