This review highlights newer insights into possible pathogenic mechanisms, clinical features, and treatment of primary pulmonary hypertension. A disease once believed to be found only in younger women, it has now been well documented to occur in both the young and elderly, with a female to male distribution of approximately 1.7:1 at all ages. Several possible etiologic mechanisms have recently been elucidated. Evidence has been forthcoming suggesting a possible role for thromboxane being produced by the pulmonary vascular bed, an underlying abnormality in clot lysis, the presence of antinuclear antibodies which could represent a collagen vascular disorder involving the lung, and a potential aggravating role of female hormones. Unfortunately, the major frustration with primary pulmonary hypertension remains its treatment. Some investigators suggest that anticoagulation may have beneficial effects on long-term survival, although this remains controversial. Most of the recently published articles on therapy have dealt with the use of vasodilators. A careful review of the effectiveness of vasodilators in these patients has failed to show that their chronic use alters either the patient's clinical course, survival, or the disease process itself. It does appear, however, that sustained beneficial effects can be realized in some patients if a substantial reduction in the pulmonary artery pressure is achieved with drug treatment. A thorough understanding of the physiologic characteristics of the pulmonary vascular bed is necessary in order to avoid misinterpreting the effects of vasodilators, which can also be detrimental. The development of vasodilators that are more specific for the pulmonary vascular bed may lead to better clinical results. Strategies for making an earlier diagnosis, however, may be equally important in our attempts to improve the prognosis.