The aim of this study was to evaluate tissue oxymetry dynamics in patients with different initial tissue oxygenation levels and to analyze the relation of these data with the perioperative period flow peculiarities. METHODS 92 patients undergoing on-pump myocardium revascularization or valve replacement were included in the study. Regional oxygenation in all patients was monitored with FORE-SIGHT Laser Tissue Oximeter. Sensors were located in the right hemisphere projection and on right forearm. Tissue (StO2) and cerebral (SctO2) oxygenation data were analyzed before anaesthesia start, before CBP on 45th -minute of CPB and in the end of the operation. At these stages also was performed standardized time (3 minutes) vessel occlusion test (VOT). RESULTS None patients had episodes of StO2, decrease below the critical level during the operation, that allows to talk about central haemodynamics stability during the study. 1st group - patients with initial StO2, below 70% (n=19). In this group StO2, remain low throughout the operation. 2nd group- patients with initial StO2, over 70%, but before CPB decreased below 70% (n=49). 3rd group - patients with high StO2, throughout anaesthesia. VOT data confirmed tissue oxygenation disturbances in Ist and 2nd groups. In st group oxygen reserve (OR) was lower than in other groups and at the end of the surgery - lower than initial one. In 2nd group OR decreased significantly before CPB and during CPB didn't differ from 1st group. In 3rd group OR during anaesthesia was higher, than in 1st and 2nd group, but decreased by the end of the surgery. Lactate level after CPB doesn't exceed the upper limit, however, it's level was higher in the 1st and 2nd group than in the 3rd group. Central vein saturation in 3rd group was higher than in the Ist and 2nd group at all stages, except for operation start. Lower StO2, levels in 1st and 2nd group were accompanied with extension of ALV ICU length-of-stay and hospitalization. RESUME: Tissue oxymetry may be useful for regional oxygenation assessment during anesthesia. There is a decrease in tissue oxygenation and oxygen reserve of peripheral tissues during on-pump cardiosurgery The low tissue oxygenation level during preperfusion period may be a predictor for early postoperative complications.