A reciprocal translocation involving the short arms of chromosomes 7 and 11, t(7;11)(p15;p15), was found in nine patients including eight with acute myelogenous leukemia (AML) and one with Philadelphia (Ph1) chromosome-positive chronic myelogenous leukemia (CML) in blastic crisis. Although a similar chromosome rearrangement has previously been reported in five patients, including three with AML and two with CML, the 7p breakpoint in some of these cases was slightly different from that detected in our patients. Notable cytogenetic and clinicohematologic findings in our patients and those reported in the literature were as follows: (a) t(7;11) occurred in myeloid leukemia, predominantly AML with subtype M2, and occasionally in other AML subtypes and in CML with or without Ph1 chromosome; (b) t(7;11) frequently occurred as the sole chromosome abnormality; (c) most patients showed a low neutrophil alkaline phosphatase score; and (d) Auer rods were present in leukemic cells of most cases including Ph1-positive CML. Our findings suggest that a t(7;11)-associated leukemia constitutes a subgroup of myeloid malignancy involving maturing leukemic cells.