Chromosome translocations found in hematologic malignant diseases are correlated with the cytologic and histologic features of the neoplastic cells as well as with clinical features, such as the patient's age, response to therapy and prognosis. Thus, the 8; 21 and 15; 17 translocations, respectively, are associated with acute myeloblastic and acute promyelocytic leukemias. Likewise, the 8q24 translocations including 8; 14, 2; 8, and 8; 22 translocations seen in Burkitt's lymphoma, and the 1; 19 and 11; 14 translocations seen associated with pre-B-cell and T-cell leukemias, respectively, are examples of similar correlations with regard to lymphoproliferative disorders. With the exception of the cases of 9; 22 (Ph1) and 11q23 translocations, each of which is found in both myeloid and lymphoid neoplasms, any one abnormality is rarely encountered in association with both categories of malignancy. Recent studies indicate that, with regard to many of the known chromosome translocations, the break occurs at a point close to the location of a specific cellular oncogene. Thus, c-myc and c-abl, which reside in 8q24 and 9q34, respectively, are known to undergo rearrangement in cases of 8q24 and 9; 22 translocations. These rearrangements have been proved to give rise to the production of an abnormal protein, which seems to cause the malignant transformation of cells with such chromosome translocations. Chromosome translocations are now believed to be directly related to oncogenesis through the mechanism of activation of the cellular proto-oncogene.