Burkitt's lymphoma (BL) and its variants, including Burkitt-like lymphoma (BLL), can be difficult to distinguish morphologically and immunophenotypically from diffuse large B-cell lymphoma (DLBCL). Because the treatment of BL differs markedly from that of other types of non-Hodgkin's lymphoma (NHL), exact pathological diagnosis is crucial. We report 2 cases of patients with BL initially diagnosed as DLBCL. Due to clinical features typical of BL, long distance polymerase chain reaction (PCR) for detecting the t(8;14) translocation involving the c-myc proto-oncogene was performed on ascites lymphoma cells. Re-evaluation by a reference hematopathologist, together with long distance PCR in both patients revealing the t(8;14) translocation, resulted in diagnosis modification to BL and BLL. Consequently, the patients were treated with intense high-dose chemotherapy regimens including central nervous system (CNS) prophylaxis, and complete remission was initially achieved in both patients. Both BL and BLL should be considered in the differential diagnosis of DLBCL if abdominal spread with ascites and metabolic disorders are present. Long distance PCR analysis of ascites lymphoma cells for the detection of the BL-typical c-myc rearrangement offers a convenient and rapid possibility of diagnosis verification in atypical or borderline cases of BL.