Persistence of minimal residual disease (MRD) is the most important adverse prognostic factor for patients with acute lymphoblastic leukemia (ALL), irrespective of classical risk factors identified at onset. Detection of MRD in the post-induction phase of ALL treatment is the only generally accepted risk factor that is considered a direct indication for inclusion in the treatment of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Several studies in recent years have shown that MRD determined before transplantation may increase the risk of disease relapse in ALL patients. To assess the impact of pre-transplant MRD status determined by multiparameter flow cytometry (MFC) on the long-term results of allo-HSCT in ALL patients. The study involved 98 patients with ALL in the 1st CR (n=58) and 2nd or 3rd CR (n=40) who underwent allo-HSCT in our center from November 2015 to July 2021. The median follow-up was 11.7 (1-65.5) months. To determine MRD, 12-color MFC was performed on bone marrow samples obtained before allo-HSCT. The probabilities of OS and DFS and the probability of relapse (PR) were estimated using the Kaplan-Meier method. The Cox proportional hazards model was used to assess the influence of various independent factors (donor type, conditioning regimen, graft source, GVHD prophylaxis, pre-transplant MRD status, age) on PR. Ten patients in 1st CR and 14 patients in 2nd or 3rd CR were identified as MRD+ before allo-HSCT. OS of MRD+ patients in 1st CR did not significantly differ from MRD- patients, although it was worse (28% vs. 78%, P=0.09). Significant differences were found in the DFS of MRD+ and MRD- patients (20% vs. 56%, P=0.0317); PR was also significantly higher in MRD+ patients (73% vs. 22%, P=0.0079). OS, DFS, and PR in MRD+ and MRD-patients were comparable. In our study, the presence of MRD before allo-HSCT (HR=3.858) was an independent factor influencing the probability of relapse. MRD determined by MFC is an independent predictor of the risk of relapse after allo-HSCT in ALL patients. Detection of MRD in patients with ALL in 1st CR before allo-HSCT is necessary to stratify the risk and identify patients who need post-transplant therapy.