To the Editor: In the study on multiple myeloma by the European Group for Bone Marrow Transplantation (Oct. 31 issue)1 the principal component of treatment (in 81 of 90 patients) was total-body irradiation. Those involved in transplantation tend to forget that it is not the bone marrow transplant itself that has the potential to cure, but rather the conditioning regimen, the details of which are often only sketchily provided. The transplant itself provides the means for the patient to survive the supralethal bone marrow toxicity, with graft-versus-tumor effect probably playing a minor part. Does this matter? In our view, it.