Maple syrup urine disease, or leucinosis usually presents between the 4th and 10th day of life with neurological and gastro-intestinal symptoms. A distinctive odour of maple syrup on the child's skin or of his urine enables diagnosis to be made clinically, confirmation coming from amino-acide chromatography which reveals increased levels of the branched amino acids, leucine, valine and isoleucin in the blood and urine. The disease, untreated, is fatal, death occurring rapidly. With early diagnosis and treatment with a diet deficient in branched amino acids and purification methods the prognosis is quite good. E.E.G. appearances are clearly, therefore, of considerable interest: --burst suppression or "pseudo burst suppression" in the acute phase, suggesting severe cerebral insult and warranting amino acid chromatography. --rolandic "picket fence" waves seen between the 2nd and 4th weeks of life, which are strongly suggestive of the disease. --good correlation between clinical, biochemical and E.E.G. parameters, improvement of the last two indicating a good prognosis. --E.E.G. observation at regular intervals is justified after the acute phase to aid forecasts concerning the eventual outcome.