Background. Recent advances in the treatment of relapsed/refractory acute lymphoblastic leukemia (R/R ALL) are attributed to the implementation of immunotherapy methods which include blinatumomab, the bispecific engager of a patient's endogenous T-cells (Blincyto™, Amgen®) (BC). Aim. To assess BC efficacy and toxicity in the treatment of R/R ALL patients with persistence of minimal tumor clone before and after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Materials & Methods. The trial included 66 B-ALL patients with CD19+ aged 18 to 72 years, 23 (35 %) of them with measurable minimal residual disease (MRD+) and 43 (65 %) with R/R ALL. In 18 (27 %) patients BC was administered after prior allo-HSCT. Results. In the overall group 2-year overall survival (OS) and disease-free survival (DFS) in patients with response to BC treatment were 53 % and 38 % respectively. In the R/R ALL group complete remission (CR) was achieved in 29 (67 %) patients including 24 (83 %) patients with negative MRD. CR rate was higher in standard cytogenetic risk group (73 %) in comparison with high-risk group (59 %). In patients with more or less than 50 % blast cells in bone marrow CR rate was 85 % and 61 %, respectively. When BC was administered after prior allo-HSCT and without it CR rate was 80 % and 60 %, respectively. In R/R ALL patients with response to BC 2-year OS and DFS were 40 % and 26 %, respectively, in the MRD+ group of ALL patients they were 66 % and 51 %, respectively. Relapse rate was lower in the group with allo-HSCT than in the group without it, i.e. 21 % vs. 55 %. Adverse events of grade 3-4 were observed in 25 (38 %) patients. In 11 (16 %) patients BC therapy had to be discontinued, in 5 (7 %) patients it was terminated prior to the scheduled date. Conclusion. BC efficacy is higher in the MRD+ group and in R/R ALL patients with smaller tumor mass. BC treatment after allo-HSCT yields remissions in most patients and can be combined with immune-adoptive therapy.