An 8;14 chromosome translocation with the break points t(8;14(q11;q32) is described in bone marrow cells of a patient with null cell terminal deoxynucleotidyl transferase (TdT)-positive acute lymphoblastic leukemia. The patient, who is dysmorphic and mentally retarded, ha a normal 46,XY constitutional chromosome karyotype. A review of the more usual cytogenetic findings in this type of leukemia and a comparison of B-cell lymphoproliferative cytogenetic associations are presented.