Before prostacyclins became available, lung or heart/lung transplantation was the only effective treatment for patients with primary pulmonary hypertension (PPH) who deteriorated under supportive medical treatment. Unfortunately, acute and chronic rejections occur in a large number of cases, limiting the average survival to 4.5 yrs. A female patient, age 35 yrs, was diagnosed with PPH and underwent single lung transplantation. Despite aggressive immunosuppressive therapy, the patient had several episodes of acute rejection. Eventually, chronic rejection with bronchiolitis obliterans developed. After 5 yrs, the donor lung was no longer functional. The patient was in New York Heart Association (NYHA) class 4, had a 6-min walking distance of 50 m and a resting arterial oxygen tension (Pa,O2) of 9.8 kPa (74 mmHg) when using 3 L x min(-1) of oxygen. Epoprostenol treatment was started and the patient showed remarkable improvement. After 17 months the patient was NYHA class 2, walked 503 m in 6 min and had a resting Pa,O2 of 10.9 kPa (82 mmHg) without supplemental oxygen. In this patient, treatment with epoprostenol was effective after rejection of a single donor lung transplanted for primary pulmonary hypertension.