Although pulmonary hypertension is a well-described manifestation of systemic lupus erythematosus, there are few data regarding the pulmonary artery pressure response to exercise. We hypothesized that exercise capacity was reduced and that the pulmonary artery pressure response to exercise was abnormal in patients with systemic lupus erythematosus. To test these hypotheses, we performed Doppler exercise echocardiography in 18 patients with lupus and 10 normal control subjects. Exercise duration was significantly reduced in the patients with lupus (8.1 vs 14.4 minutes for control subjects, p < or = 0.001). Pulmonary artery pressure was significantly higher in the patients with lupus at rest and during the first two stages of exercise (p < 0.05). Cardiac indexes at rest were similar in the two groups, suggesting that increased pulmonary vascular resistance was the mechanism for the higher pulmonary pressure we observed. We conclude that abnormal exercise hemodynamics may contribute to reduced exercise capacity in patients with lupus.