Background: Haploidentical bone marrow transplantation is a life-saving procedure for patients with hematologic malignancies and other blood disorders. We aimed to assess the role of the Endothelial Activation and Stress Index (EASIX) formula, C- reactive protein (CRP), IL-6, and Ferritin in patients with cytokine release syndrome (CRS) in Haploidentical Transplants. Methods: This cohort study was performed on 49 patients aged from 10 to 60 years old, both sexes, who underwent Haplo Transplant. All patients were subjected to receiving T-cell replete haploidentical stem cell transplant utilizing post-transplant cyclophosphamide platform as graft versus host disease and graft failure prophylaxis. The conditioning regimen is reduced intensity conditioning. Results: At a cut-off point of 4.15, the specificity and sensitivity of the EASIX score in predicting the death of haploidentical bone marrow transplant (BMT) patients with CRS is 76.9 % and 60%respectively. The EASIX score, and the studied biomarkers increased significantly from baseline to day 7 of BMT (P < 0.05). There was significant difference within CRS group between EASIX score at baseline and EASIX score at CRS onset (P= 0.0003), and between serial EASIX score measurements among CRS patients (P < 0.001). Conclusions: EASIX score was a poor predictor of response to CRS severity and mortality in BMT patients. Also, inflammatory markers (IL-6, CRP and Ferritin) were not reliable to predict the response to CRS and mortality in BMT patients. EASIX score, IL-6, CRP and Ferritin have no association with outcome or CRS severity.