Fulminant cerebral oedema is an uncommon, fatal complication of diabetic ketoacidosis (DKA) in children. This study aimed to find out whether the sub-clinical compression of the brain ventricles found by an earlier study, is a general phenomenon during intravenous treatment for DKA. Four boys and four girls were examined. Blood glucose values ranged from 40 to 24.6 mmol/l, base excess -34.6 to -13.6 and capillary blood pH 6.89-7.22. The patients received fluids containing both glucose and electrolytes, and insulin intravenously. After about 10h, blood glucose was 8.7-21.8 mmol/l and base excess had decreased substantially (-9.5 to -2.9) in seven of the eight cases. Computerized tomography of the brain was then performed, and again after full recovery. Only two of the patients had an initial decrease in intercaudate distance, which exceeded the variability found in a reference group. Compression of the cerebral ventricles does not occur regularly during treatment for DKA.