A healthy twenty-month-old boy ingested a maximal dose of valproate from which about 750 mg/kg were absorbed. Cerebral coma, which lasted for twenty hrs, was followed by an undisturbed period of approximately sixteen hrs. Death from cardiorespiratory failure due to severe bronchopneumonia occurred 46.5 hrs after the ingestion of the drug. The serum valproic acid concentration reached a peak of 1061 micrograms/ml within three hours, and fifteen minutes before death it had fallen to 187 micrograms/ml. The half-life of 16.6 hrs was within the range usually found. Metabolic acidosis, hypernatraemia and hyperosmolarity could be corrected, unlike the hypocalcaemia, which developed later. Bilirubin, GOT, GPT, gamma-GT, alkaline phosphatase, blood glucose, diastase, urea, creatinine, haemoglobin as well as PT and PTT and the platelet count were all normal. Leucopenia with 1,600 per microliter developed only during the bronchopneumonial stage. The histo-pathological findings were acute hypoxic damage of the myocardium, kidneys and certain neurones of vulnerable areas of the brain (neuronal microvesiculation and tigrolysis) in addition to a severe cerebral oedema in the final stage. A morphological substrate of an acute valproate encephalopathy was not demonstrable. The liver showed no necrosis or cholostasis. The vertebral marrow was inconspicuous. All the results indicate that liver function was not impaired in spite of the initial maximal concentration of valproic acid. In all probability the patient might have survived the acute valproate intoxication had it not been for the bronchopneumonia.