Primary pulmonary hypertension (PPH) is a devastating disease with an unknown pathogenesis. Some appetite suppressant drugs are strongly implicated in the pathogenesis of PPH. Hence, we wanted to investigate the effects of dexfenfluramine, which has been newly introduced as an anorexigenic drug in Turkey, on mean pulmonary artery pressures. Sixty-six obese outpatients were placed either on dexfenfluramine, 15 mg twice a day, plus a calorie-restricted diet (Group 1) (n=42) or on a calorie-restricted diet alone (group 2) (n=24) for three months. We measured pulmonary artery pressure with echocardiography at the beginning and at the end of the study. At the beginning of the study, mean basal pulmonary artery pressures were not significantly different between the two groups (p>0.05). Although mean pulmonary artery pressures were increased in Group 1 at the end of the study period, these increases were not significant (p>0.05). Also, pulmonary artery pressure measurements in Group 2 showed no significant changes (p>0.05). Mean body weights at the outset and at the end of the study were as follows: 89.2±4.8kg and 81.1±3.2 kg (p0.05) in Group 2. In conclusion our study shows that dexfenluramine is a very promising weight reducing agent with no significant effects on pulmonary artery pressure.