Aim. To ascertain the role of some neurohumoral factors - nitric oxide (NO), ACE, histamine - in development of pulmonary hypertension (PH) in patients with interstitial lung diseases (ILD). Material and methods. A total of 32 ILD patients were examined. Of them 14 had idiopathic fibrosing alveolitis (IFA), 6 had exogenous allergic alveolitis (EAA) and 12 patients had ILD in diffuse disease of the connective tissue (ILD-DDCT). In addition to routine tests, those for NO, ACE, histamine, serotonin in plasma were performed; Doppler echocardiography and high-resolution computed tomography were conducted. In 9 patients the diagnosis was verified at thoracoscopic biopsy of the lung. The control group consisted of 16 healthy subjects. Results. The highest mean pressure in the pulmonary artery (PmPA) was registered in IFA vs EAA and ILD-DDCT patients (p < 0.001). NO concentration in plasma was higher in ILD-DDCT than in control patients. In IFA and EAA the level of NO was like in controls. Concentration of NO in plasma oflDL patients correlated with high activity of the process. No correlation was found between ACE in plasma and PmPA, ACE levels were much higher in controls than in the ILD patients (p < 0.05). Histamine levels were higher in ILD patients than in controls being the highest in ILD-DDCT. Serotonin was insignificantly higher in ILD patients than in controls. Conclusion. Damage to the endothelium of the pulmonary arteries and imbalance of neurohumoral factors may be considered as a mechanism of development and stabilization of PH in ILD patients.