We analyze the experience derived from the use of vasodilating therapy in Primary Pulmonary Hypertension (PPH) at our institution in the last ten years. Important aspects such as complications, long-term hemodynamic effects and survival are particularly emphasized. We have consecutively studied forty patients (29 females, 11 males) with a mean age of 21 +/- 1.6 years. The follow-up period is 50 +/- 8 months and the drugs used were: Hydralazine (HDL) and Nifedipine (NFD). On the basis of their hemodynamic response the patients were divided into two groups: twenty responders (R) and twenty non-responders (NR). Both groups seem to have a different clinical and hemodynamic basal profile; most of the patients in the R group had a better functional class (NYHA: I-II) than those NR (III-IV). Also, the R group had a lower basal Pp (49 vs 77 mmHg, p less than 0.05), lower Rp (17 vs 29 U/m2, p less than 0.05) and lower Rp/Rs ratio (0.59 vs 1.05, p less than 0.05). The R group has continued on long-term vasodilator therapy with NFD (n-13) and HDL (n-7) and most of them showed a significant improvement in their quality of life and still maintain a good hemodynamic response. Only minor side effects were associated with the medication. The NR group, on the other hand, has shown progressive clinical deterioration. Eight patients in the NR group and three in the R group have died. The five-year probability of survival in the R group is 86% whereas it is only 45% in the NR group. We conclude that vasodilator therapy significantly improves quality of life, with minimum untoward effects, in selected patients with PPH. The R group probably reflects a different patient population or a different stage of the disease and therefore its better long-term prognosis cannot be attributable solely to the use of these drugs.