Primary pulmonary hypertension is defined as pulmonary arterial hypertension of unknown cause. It's a diagnosis made by exclusion; all recognizable causes of pulmonary hypertension must be ruled out before the diagnosis of primary pulmonary hypertension can be made. The prognosis is poor for medical management. Recently, with the advent first of heart-lung transplantation and then of single-lung transplantation the therapeutic options have increased considerably. We discuss the characteristics of this disease and we review the literature.