&NA;Burkitt lymphoma is a distinctive type of non‐Hodgkin lymphoma that has characteristic morphologic, immunophenotypic, and molecular genetic features. Patients can have predominantly peripheral blood and bone marrow involvement. The World Health Organization has recommended that these cases should be diagnosed as the leukemic phase of Burkitt lymphoma. The authors present a case of Burkitt lymphoma in leukemic phase and discuss the differential diagnosis. The neoplastic cells of Burkitt lymphoma in Wright‐stained bone marrow aspirate smears are blasts with round nuclei, one to several small distinct nucleoli, and abundant deeply basophilic, vacuolated cytoplasm. Immunophenotypic analysis demonstrates that Burkitt lymphoma is a mature B‐cell neoplasm that expresses B‐cell antigens, CD10, and monotypic surface immunoglobulin. Cytogenetic and molecular studies demonstrate one of three characteristic chromosomal translocations: t(8;14)(q24;q32), t(8;22)(q24;q11), or t(2;8)(p11;q24). These translocations join the c‐mycgene at 8q24 with one of the immunoglobulin gene loci, either the heavy chain gene at 14q32, the &kgr; light chain gene at 22q11, or the &lgr; light chain gene at 2p11. Translocation results in overexpression of the c‐myc protein, which regulates transcription and cell proliferation.