Studies of the lesser circulation hemodynamics in 150 patients with dilatation cardiomyopathy and in 15 after heart transplantation revealed secondary postcapillary pulmonary hypertension of more than 60 mm Hg in cases with dilatation cardiomyopathy with systolic pressure in the pulmonary artery (SPPA) in 30% of patients, transpulmonary gradient (TPG) of more than 15 mm Hg and pulmonary vascular resistance (PVR) or more than 4 Wood's U in 15.3% of patients. Two stages of pulmonary hypertension in dilatation cardiomyopathy should be singled out: I with SPPA of 60 mm Hg, TPG of 15 mm Hg, and PVR of less than 4 Wood's U, and II with SPPA of more than 60 mm Hg, TPG of more than 15 mm Hg, and PVR of more than 4 Wood's U. Orthotopic transplantation of the heart is indicated for patients with Stage I pulmonary hypertension. For patients with Stage II condition prolonged inotropic and vasodilator therapy is necessary, and if it fails, heterotopic transplantation of the heart or transplantation of the heart and lungs should be resorted to. The basic characteristics of the lesser circulation reflecting the reversibility of pulmonary circulation disorders are SPPA, TPG, and PVR. Failure of prolonged inotropic vasodilator therapy may be indicative of irreversible injury to pulmonary vessels. Lesser circulation hemodynamics usually normalizes a month after heart transplantation. If TPG is less than 15 mm Hg and PVR less than 2 Wood's U, the incidence of reversible posttransplantation right-ventricular insufficiency depends on SPPA pretransplantation level. Mortality because of right-ventricular insufficiency was 8.33%. One-year survival after heart transplantation is related to preoperative TPG and PVR values.(ABSTRACT TRUNCATED AT 250 WORDS)