Central pontine myelinolysis (CPM) is a demyelinating condition of the central pons with or without associated foci of demyelination in extrapontine areas. We present a case of partial ornithine carbamoyl transferase deficiency in a 5-year-old girl which was complicated by CPM. The patient was a previously undiagnosed girl who presented with mild hyperammonemic encephalopathy with a maximum plasma ammonia level of 376 microM on admission. Laboratory testing established the diagnosis of OCT deficiency, and therapy with hydration and protein restriction was successful in returning the plasma ammonia levels to normal. Five days after correction of her hyperammonemia, the patient developed intractable seizures and coma. Serial MRI scans of the brain revealed the evolution of the characteristic findings of CPM. Plasma ammonia and electrolyte concentrations were well controlled throughout this time. This represents the first description of CPM in a patient with a urea cycle defect.