We describe a 30 year old woman who presented with thyroid storm. She had non-specific symptoms and few clinical signs of hyperthyroidism despite markedly raised thyroid hormone concentrations. Soon after admission her behaviour became abnormal and her level of consciousness deteriorated. Despite the rapid restoration of thyroid hormone concentrations to normal using conventional therapies, and correction of hypoxia resulting from acute pulmonary oedema, her level of consciousness did not improve. Cranial CT scanning revealed extensive bilateral basal ganglia infarction, a previously unreported complication of thyroid storm. This observation suggests that thyroid storm may predispose to hypoxic neurological damage.