Aim. To describe hemodynamic and clinical changes in patients with elevated mean pulmonary artery pressure (MPAP) >30 mm Hg during exercise and the impact of bosentan therapy on stress-induced pulmonary hypertension (SIPH). Subjects and methods. The study included 19 patients with systemic sclerosis (SDS) in whom possible causes of pulmonary hypertension (PH) (lung and left heart injuries and thromboembolism) were excluded. All the patients underwent pulmonary artery catheterization at rest and during exercise. The hemodynamic (right atrial pressure (RAP), systolic and diastolic pressure, MPAP, pulmonary artery wedge pressure (PAWP), cardiac output (CO) by a thermodilution technique), clinical (demographic, immunological, and instrumental) parameters were analyzed and the risk of pulmonary arterial hypertension (PAH) was also calculated; 5 patients with SIPH received 16-week bosentan therapy according to the conventional regimen. Results. Ten of the 19 patients were at increased risk for PAH in accordance with the DETECT scale, but no signs of PH at resting catheterization were found in anybody. In 5 patients, MPAP, was in the range from 21 to 24 mm Hg; in 9 (47%) patients were found to have SIPH, a median MPAP of 35 (32; 41) mm Hg. Seven patients had no diagnostic changes during exercise; 3 patients could not perform an exercise test. There were correlations between MPAP and DETECT risk scores (p<0.05). The patients with SIPH had significantly higher levels of resting MPAP and exercise pulmonary vascular resistance (PVR) and PAWP. The calculated DETECT risk was significantly higher in the SIPH group. The level of uric acid was also higher in the SIPH group (p<0.05). There were no changes in NT-proBNP levels, telangiectasias and anti-centromere antibodies, and EchoCG and lung test results. During 16-week bosentan therapy, there was a significant decrease in MPAP and transpulmonary gradient during exercise, but PVR, MPAP/CO ratio and NT-proBNP levels tended to decrease. Conclusion. In the patients with SDS, SIPH may be a stage of pulmonary vasculopathy that precedes the development of clinical PAH. The use of current PAH-specific drugs used at the preclinical stage of the disease may substantially improve lifetime prognosis in patients with SDS-associated PAH.