Pulmonary hypertension (PH) in systemic lupus erythematosus (SLE) is associated with an unfavorable prognosis. We investigated the characteristics of SLE patients with PH. The patients with a pulmonary artery systolic pressure more than 30 mmHg at rest on echocardiogram were diagnosed with PH. Echocardiography was done only in patients with clinical or radiological evidence suggesting PH. Right heart catheterization was not performed. We identified 10 SLE patients with PH between 1980 and 2000. We compared their clinical and laboratory parameters with those of 97 consecutive SLE patients without PH. Nine of the ten patients with PH were females. The mean age at the time of SLE onset was 25.2 +/- A 6.9 years; the mean duration of follow-up was 93.4 +/- A 52.8 months, and the interval between the onset of SLE and PH diagnosis was 9.0 +/- A 4.6 (5-21) years. Antiphospholipid antibody positivity was significantly higher in the PH group (80 vs. 36%; p < 0.05), but there was no significant difference between two groups in regard to secondary antiphospholipid syndrome. The frequency of Raynaud's phenomenon was higher in PH group (60 vs. 27%; p < 0.05). Renal involvement (80 vs. 43%; p < 0.05), neuropsychiatric involvement (40 vs. 7.2%; p < 0.005) and serositis (70 vs. 14.4%; p < 0.001) were significantly more frequent in the PH group. The mean damage score in patients with and without PH were 4.0 +/- A 2.4 and 0.4 +/- A 1.0, respectively (p < 0.001). Four patients with PH died during the follow-up. This study reveals that the presence of PH defines a subgroup of patients with a severe disease and increased mortality. Antiphospholipid antibodies and Raynaud's phenomenon may contribute to the pathogenesis of PH. We recommend that all patients with SLE, especially those positive for antiphospholipid antibodies and/or with signs of Raynaud's phenomenon should be regularly evaluated for the development of PH.