Pyridoxine-dependency is a rare autosomal recessive disorder causing a severe seizure disorder of prenatal or neonatal onset, psychomotor retardation and death in untreated patients. Treatment requires life-long supplementation with pyridoxine (vitamin B6). The underlying defect is unknown, and there is no biological marker for the disease. Clinical diagnosis is often delayed and severe neurological sequelae are common. This article summarizes both clinical and therapeutic aspects.