Objective: It was aimed to evaluate factors contributing to mortality in the post-transplantation period and determine the relative risk of death caused by these factors in patients who underwent allogeneic hematopoietic stem cell transplantation. Material and Methods: Outcomes of 184 patients who underwent stem cell transplantation were retrospectively assessed. The patients were classified by considering the factors such as diagnosis, health status at the time of transplantation, time of transplantation, time between diagnosis and transplantation, histocompatibility, donor-recipient gender compatibility, amount of CD34 stem cell which was given, preparation regimes and risk status at the time of diagnosis. Outcomes were analyzed statistically by Kaplan-Meier survival analysis, Cox regresion test and multivariate regresion test. Results: When confounding factors of transplant-related mortality were assessed using multivariate regression analysis, recurrent disease development was shown to be the most significant factor affecting mortality (hazard rate: 3.12; 95% CI: 2.02-4.82; p<.001). The other factors affecting mortality were chronic graft versus host disease (hazard rate: 1.92; 95% CI: 1.19-3.09; p=.008), high-risk status of patients with acute leukemia at diagnosis (hazard rate: 2.47; 95% CI: 1.47-4.14; p<.001) and acute graft versus host disease (hazard rate: 1.78; 95% CI: 1.10-2.88; p=.019). Conclusion: It is very important for each stem cell transplantation center to determine the risk groups for transplant-related mortality and morbidity and outcomes in their own patient groups.