Glucose transporter 1 deficiency syndrome is emblematic of a brain energy failure syndrome. Energy failure also results from other genetically determined metabolic disorders, such as hypoglycemic syndromes, hypoketonemic syndromes associated with fatty acid oxidation defects, glycolytic enzymopathies, and mitochondrial defects. Glucose transporter 1 deficiency syndrome is particularly illustrative of this group of disorders and produces an infantile-onset epileptic encephalopathy that responds to a ketogenic diet. The electroencephalographic correlate is distinctive and emerges as a 2.5- to 4-Hz spike-wave discharge in late infancy to early childhood. Infantile apnea and oscillatory eye movements reminiscent of opsoclonus may be the earliest signs of this condition. Mutations of the GLUT1 gene are causative and transmitted as an autosomal dominant trait. Thioctic acid is a glucose transporter 1 activator, whereas barbiturates and methylxanthines are glucose transporter 1 inhibitors. The ketogenic diet is effective treatment for glucose transporter 1 deficiency syndrome and pyruvate dehydrogenase deficiency. It also should benefit patients with neurologic symptoms resulting from a glycolytic enzymopathy.