Multiple myeloma, despite the recent advances in treatment, remains an incurable disease with a poor prognosis for the majority of patients. Allogeneic hematopoietic stem cell transplantation, especially given the development of novel reduced-intensity conditioning protocols, is an appealing alternative to the current standard of care because it, through the graft-versus-disease effect, offers a stronger anti-tumor effect and the possibility of cure. Our research included 13 patients suffering from multiple myeloma and plasma-cell leukemia who underwent allogeneic hematopoietic stem cell transplantation. All of the patients had undergone an autologous stem cell transplantation before the allogeneic one. The overall survival of the patients two years after the allogeneic transplantation was 37.5%, while the progression-free survival two years after the allogeneic transplantation was 33.3%. The majority of the studies that have been published, including ours, have not shown a clear advantage of the allogeneic transplantation in comparison with the standard of care, primarily owing to the high treatment-related mortality. Taking into consideration a large number of new drugs in multiple myeloma treatment, some of whom are showing high treatment efficacy, as well as the aforementioned modest results of the allogeneic stem cell transplantation, the role of allogeneic transplantation in the treatment of multiple myeloma is becoming less and less relevant to most of the patients.