Estimates of branched chain amino acid concentrations in plasma and, or, serum, urine, cerebrospinal fluid, formalin-fixed cerebral tissue and the associated formalin, provided evidence for a diagnosis of branched chain keto acid decarboxylase deficiency in five polled Hereford calves. The similarity of the clinical signs of dullness, recumbency and opisthotonos, and the observation of severe status spongiosus within the central nervous system, indicated that this condition had probably affected seven other newborn calves. It is suggested that this condition is analogous to branched chain keto acid decarboxylase deficiency or maple syrup urine disease of children.