High-resolution proton nuclear magnetic resonance spectroscopy was used to study human urine obtained from 10 normal babies and twenty babies with various degrees of neonatal asphyxia, respiratory distress syndrome (RDS), and meconium aspiration syndrome (MAS). All sick babies showed different degrees of oxygen deficiency, indicated by an obvious increase of the lactate signal level in the urine spectra. Changes in the concentration of other urinary metabolites produced from the citric acid cycle were also observed. In extremely serious cases, the signals of some of the major components, including citrate, ac-ketoglutarate, and succinate, simply disappeared. The spectra of urine, serum, and CSF of an infant suffering from SIDS showed common characteristics of the metabolites.