A 47-year-old man relapsed with accelerated phase CML 19 months after a T cell-replete unrelated BMT. Three donor leukocyte infusions (DLI) from the original donor resulted in durable complete hematological and cytogenetic remission. Moderate GVHD developed but was steroid responsive. This report suggests that DLI can be administered safely to patients relapsing after unmodified unrelated allografts. In the patient described, DLI exerted an antileukemic effect sufficiently potent to reverse accelerated phase disease.