Acute bilineal leukemias are rare and are commonly associated with t(9;22) and MLL abnormalities. Herein, we report a pediatric case of bilineal T/myeloid acute leukemia associated with del (9q)(q13q22) and TLX3/BCL11B fusion due to the cryptic t(5;14)(q35;32). FISH studies confirmed the TLX3/BCL11B fusion in both the myeloid and lymphoid blasts, while the 9q deletion was restricted to the lymphoid component. Optimal therapy for such patients remains controversial and it is not clear if they should be treated with ALL or AML-based chemotherapeutic regimens. Our patient has been in extended remission following ALL-based chemotherapy and a matched unrelated cord blood transplant. Pediatr Blood Cancer 2011;56:467–469. © 2010 Wiley-Liss, Inc.