FIELD : medicine.SUBSTANCE : invention relates to medicine and can be used to identify an effective cryoprotector by the cytochemical index of the content of leukocyte alkaline phosphatase (LAF) of autologous blood. To do this, a portion of patient’s fresh autologous blood is exfused before the start of cryohemotransfusion therapy. Blood is stabilized with sodium citrate solution. In a control sample (CS) additives of cryoprotectors is not dispensed. In the check samples (ChS) one by one is equal dose of the tested cryoprotectors dispensed, mixed at +37?°C for 4 hours. Drops of prepared ChS and CS are applied in a volume of 4 mcl on glass slides and smears are made. Drugs for the detection of LAF in segmented neutrophils according to the method of Kaplow azo coupling are prepared. Comparative study of the average cytochemical coefficient (ACC) of LAF for segmented neutrophils in the ChS and CS is carried out. Tested cryoprotector is assessed as effective for the patient with ACC LAF ChS values equal to the ACC LAF CS values. Tested cryoprotector is assessed as ineffective for the patient at values of ACC LAF ChS, different from ACC LAF CS.EFFECT : invention allows to identify in vitro an optimal cryoprotector at the preclinical stage of cryohemotransfusion therapy and reduce the risk of post-transfusion complications in patients.1 cl, 1 tbl, 3 ex