We report three cases of chromosome 13 rearrangements as additional abnormalities in two patients with Burkitt lymphoma (BL) and one with type 3 acute lymphoblastic leukemia (ALL). Involvement of chromosome 13 has been reported most often as 13q+, without identification of the supplementary chromosomal material; in our three cases with 13q+, we identified two duplications: dup(13)(q13q22) and dup(13)(q21q22).