Clonal chromosome changes have been found in two patients with Waldenström's macroglobulinemia (WM). In one, the changes were only numerical: trisomy 3, trisomy 18, and monosomy 21. In the other, both numerical and structural changes were observed, among which t(8;14) with breakpoints (q24;q32), similar to those found in Burkitt's lymphoma, was the most relevant. This association between a new lymphoproliferative process and the Burkitt-type t(8;14) is stressed.