A 6-year-old patient with hydrocephalus who underwent revision of a ventriculo-atrial shunt is described. Anaesthesia was complicated by the occurrence of systemic hypertension and arterial hypoxaemia. The patient was subsequently found to have pulmonary hypertension secondary to recurrent pulmonary thromboembolism. The pathophysiological mechanisms for the patient's deterioration are discussed and the anaesthetic management of children with pulmonary hypertension is outlined. It is concluded that patients with a ventriculo-atrial shunt who present for surgery should be screened carefully for the presence of pulmonary hypertension.