Fenfluramine derivatives (Fds) are a well-established risk factor for primary pulmonary hypertension (PPH). We compared 62 Fd-PPH patients (61 women) evaluated in our center between 1986 and 1997 with 125 sex-matched PPH patients nonexposed to Fd referred during the same period (control PPH). In the Fd-PPH group, 33 patients (53%) used dexfenfluramine alone, 7 patients (11%) used fenfluramine alone, and 5 patients (8%) used both drugs. In 17 cases (27%), Fd use was associated with that of amphetamines. Most of the exposed patients used Fd for at least 3 months (81%). The interval between the onset of dyspnea and that of drug intake was 49±68 months (27 days to 23 years). At the time of diagnosis, Fd-PPH and control PPH were similar in terms of New York Heart Association functional class and symptoms. The two groups significantly differed only in terms of age (50±12 vs 40±14 years) and body mass index (28±6 vs 23±4). The two groups displayed similar severe baseline hemodynamics (total pulmonary vascular resistance: 32±12 vs 31±12 IU/m2), but the percentage of responders to acute vasodilator testing was higher in control PPH (27% vs 10%, p<0.01). As a result, more patients were treated with oral vasodilators in the control PPH group (36% vs 16%, p<0.01) and long-term epoprostenol infusion was more frequently used in the Fd-PPH group (52% vs 31%, p<0.01). Overall survival was similar in the two groups with a 3-year survival rate of 50%.