Pulmonary hypertension was diagnosed in a patient with SLE after her 5th delivery. Time of onset and absence of thromboembolism and severe interstitial lung disease suggested primary pulmonary hypertension. Administration of vasodilators did not decrease pulmonary artery pressure which amounted to 82/30 mm Hg. Cyclophosphamide infusions, 0.5 g/m2 monthly for 6 months followed by once/3 months, in combination with 7.5 mg prednisolone daily resulted in decrease of pulmonary artery pressure to 66/34 mm Hg after 6 months of treatment persisting for 30 months. Intermittent infusions of cyclophosphamide with low dose prednisolone may be effective in primary pulmonary hypertension in SLE, suggesting an immune mediated pathogenesis.