Cytogenetic findings in leukemia can be used in the diagnosis, prognosis, and in the definition of different subgroups. The most common chromosome abnormalities associated with mature B-cell acute lymphoblastic leukemia (ALL) are t(8;14), t(8;22), t(2;8), and partial duplication of 1q. Various abnormalities involving chromosome 1 have also been reported in ALL. We present a 16-year-old male with mature B-cell ALL whose cytogenetic analysis of bone marrow showed the karyotype of 46,XY,t(8;14)(q24;q32), -15,der(1;15)(p10;q10). The case presented here carries one of the most common abnormalities, t(8;14) (q24;q32), and a new rearrangement, der(1;15)(p10;q10), which has not been described to date in mature B-cell ALL. (C) 2002 Elsevier Science Inc. All rights reserved.