Analysis of a variant translocation t(11;17) in a case of acute promyelocytic leukemia (APL) led to discovery of a novel zinc finger gene, PLZF, fused to the retinoic acid receptor-α (RARα) gene. We reviewed the clinical and molecular features of five additional patients with t(11;17)- associated APL. The clinical course of three patients was characterized by early death and three experienced disseminated intravascular coagulation. Morphologically all of the patients fell in a unusual morphologic spectrum of APL, with features intermediate between M2 and M3 AML. All six patients had PLZF-RARα gene fusion as detected by reverse transcription/polymerase chain reaction assay, Southern blotting, or pulsed-field gel electrophoresis. Five of the six patients failed to achieve complete remission after initial chemotherapy or differentiation therapy with all-trans retinoic acid (ATRA). A sixth patient responded to initial chemotherapy, but on relapse failed to respond to ATRA. When tested in vitro, cultured cells from three of the patients failed to differentiate in response to ATRA. APL associated with t(11;17) and fusion of the PLZF and RARα genes is a discrete clinico- pathologic syndrome with a distinctly worse prognosis than t(15;17) APL.