Chronic thromboembolic pulmonary hypertension (CTEPH) may develop as a consequence of silent or symptomatic but unrecognized and not treated thromboembolic events, however, its course is little known. A prospective study with once a year evaluation of survival, Doppler-derived systolic pulmonary artery pressure (PASP), functional NYHA class, and exercise tolerance in a group of 26 newly diagnosed CTEPH patients aging 37 to 82 years with mean pulmonary artery pressure (MPAP) ranging from 21 to 86 mmHg was undertaken. None of patients underwent pulmonary endarterectomy (10 patients had distal embolism, 4 patients had proximal embolism and MPAP < 30 mmHg, 12 patients with proximal embolism and MPAP>30mmHg did not accept risk of surgery). After starting anticoagulation, the 3-year survival in 13 patients with baseline MPAP < 33mmHg was 100%. In these patients PASP decreased < 40 mmHg after 1,2 and 3 year in seven, nine and in all but one patient, respectively. NYHA class improved in 12 patients and trend to increase number of METS during exercise test (p = 0.09) was found. The survival rate for 13 patients with MPAP > 33 mmHg was respectively 77%, 62% and 46%. 3 patients with MPAP > 69 mmHg died before 1 year of follow-up. In summary, patients with newly diagnosed CTEPH preceded by silent or unrecognized thromboembolic events, with MPAP > 33mmHg should be promptly operated whereas patients with MPAP < 33 mmHg, can be initially treated by anticoagulation alone and should be followed regularly with echocardiography, assessment of NYHA class and exercise tolerance.