To evaluate the significance of karyotypic evolution of tumor cells with an 8;14 translocation [t(8;14)(q24;q32)], we examined the clinicopathologic features and immunologic phenotypes of nine Japanese patients with various types of B-cell malignancy with the translocation. All these patients had structural rearrangements of the long arm of chromosome No. I (Iq) in a stem line or the subline of tumor cells with a t(8;14). The rearrangements were composed of a translocation involving Iq with other chromosomes and a tandem duplication of Iq, and they were exclusively associated with a partial trisomy for Iq. Two patients with diffuse large-cell lymphoma, whose tumor cells did not express surface immunoglobulins (s-Ig), had the Iq translocation in their highly complex karyotypes. Tumor cells from the other seven patients expressed s-Ig and the karyotypes were relatively simple. Among these patients, the Iq translocation was found in two patients with Burkitt's lymphoma, and the Iq duplication were observed in a stem line or the sublines from four patients with Burkitt's lymphoma-leukemia and one each with small non-cleaved-cell or diffuse large-cell lymphoma. Except for one patient in the stage of IE, these patients had a poor prognosis because of the clinical conversion of extranodal metastases in the earlier disease phase. These findings are compatible with those of Western patients with a t(8;14). Therefore, tumor cells marked primarily with a t(8;14) could have "major routes" in the karyotypic evolution, for which potentials should be recognized as clinical risk factors, and the morphologic presentation and the expression of surface immunoglobulins may be associated with the process of karyotypic evolution.