In 1996 the total number of prescriptions of the appetite depressant drugs fenfluramine and phentermine exceeded 18 million in the United States. Clinical observation and experimental evidence back in the early 1980's showed that these drugs can cause a pulmonary hypertension. We report the case of a 30-year old woman with a history of seven month medication with dexfenfluramine. She developed severe pulmonary hypertension and right heart failure during late pregnancy. She died of septicemia with multiorgan failure 4 days after cesarean section. Pulmonary hypertension has been reported in association with treatment with fenfluramine and dexfenfluramine. These drugs may cause the increased precapillary resistant pressure through the vasoconstrictor action of serotonin. The typical histological finding is a plexogene pulmonary arteriopathy and valvular heart disease. After these observations the drugs were withdrawn.