Serial PCR analysis for patients who received HLA-identical sibling marrow grafts for the treatment of CP CML. (A) Patients who have not relapsed and therefore have not been treated with DLI. (B) Patients who were treated with DLI for relapsed disease. (•) Patients testing positive for the presence of the bcr/abl RNA transcript. (○) Patients testing negative for the presence of the bcr/abl RNA transcript. Arrows indicate time of relapse posttransplant. (i) Denotes the time of first donor leukocyte infusion.