Aim of investigation is a study of the blood flow fractional reserve measurement significance for optimization and assessment of the coronary artery lesion endovascular correction effectiveness.Materials and methods. An investigation of pressure in the coronary arteries was accomplished in a roentgenosurgical operating room with a use of the RADI Analyzer apparatus (Axle International). The results of endovascular interventions in 67 patients with the coronary artery bifurcation lesions are analyzed. An assessment of the coronary arteries in one group of patients was made on a basis of the selective coronarography data, and a measurement of a blood flow fractional reserve was made in the other group of patients beside a coronarography.Results. A circulation fractional reserve measurement is more significant for a bifurcation lateral branch state assessment because a negative correlation of its meanings and the selective coronarography results is established; the non-coincidences of the stenosis significance are mostly observed in the border stenosis group (II stage).