Primary pulmonary hypertension is considered a fatal illness, with survival typically of less than four years, although survival of more than 10 years has been well documented. To assess the characteristics of patients with primary pulmonary hypertension who survive versus those who do not, 12 patients with primary pulmonary hypertension were followed, and their clinical course was documented with serial catheterization. The survivors, four male and three female, had their illness for a mean of 5.2 +/- 2 years from the time of initial catheterization, with six of the seven alive at the end of the follow-up period. The five nonsurvivors, all female, had a mean survival of 0.3 +/- 0.2 years. The nonsurviving group had significantly higher right atrial pressures (17 +/- 6 versus 6 +/- 2 mm Hg), lower cardiac indexes (1.2 +/- 0.1 versus 2.3 +/- 0.5 liters/minute/m2) and stroke volume indexes (12 +/- 7 versus 30 +/- 5 ml/beat/m2), and higher systemic resistances (64 +/- 13 versus 43 +/- 14 units) and pulmonary resistances (57 +/- 31 versus 20 +/- 4 units). The pulmonary artery pressure did not significantly differ between the groups. Using regression analysis, it was found that stroke volume index and right atrial pressure were the best independent predictors of survival, with a coefficient of determination (r2) of 83 and 72, respectively. When the initial and most recent catheterization data were compared among the survivors, no significant differences were found. Determining the stroke volume index and right atrial pressure of patients with primary pulmonary hypertension at the time of their initial presentation should help in predicting their clinical course.(ABSTRACT TRUNCATED AT 250 WORDS)