Primary pulmonary hypertension (PPH), a disease most common in young and middle aged people, is associated with progressive dyspnea and poor prognosis. Available treatments have been shown to improve symptomatology and survival. However, treatments are quite costly and may have potentially life threatening side effects. This proposal is a cross sectional, observational study of health related quality of life (HRQOL) and health state preferences (utilities) in patients with primary pulmonary hypertension prior to initiation of prostacyclin therapy and while on therapy. HRQOL is assessed by means of a generic questionnaire (the Nottingham Health Profile) and a disease specific questionnaire (Chronic Heart Failure Questionnaire). Utilities are determined by the standard gamble technique. It is hypothesized that HRQOL measures and utilities will improve in patients receiving prostacyclin therapy. Utilities obtained from the first part of this study are combined with survival data from the literature to determine quality adjusted life years for PPH patients. In the second part of the study a decision model is used to determine the costs, life years, quality adjusted life years, and incremental cost effectiveness ratios of four treatment strategies for pulmonary hypertension. It is hypothesized that despite high costs and potential complications, prostacyclin therapy is highly cost effective for the treatment of PPH.