During B cell development, immunoglobulin heavy chain (IgH) variable region (VH) genes are rearranged and expressed in a programmed manner and accumulating evidence suggests recurrent utilization of developmentally restricted VH genes in malignant B lymphoid populations. We have used polymerase chain reaction gene amplification in conjunction with a panel of VH family-specific amplimers to directly compare the repertoire of VH region rearrangement in mature, CD5+ B cell chronic lymphocytic leukemia with that in immature, CD5 B lineage acute lymphoblastic leukemia. The results revealed a diverse pattern of VH family utilization common to both disease groups in which VH regions most proximal to the IgH joining locus were preferentially rearranged relative to their family sizes with recurrent utilization of several known developmentally restricted VH genes in close to germ-line configuration. These results indicate that biased VH family usage is independent of tumor cell phenotype in B lineage leukemias. This bias may reflect similar stages or compartments in normal B lymphopoiesis from which diverse types of B cell malignancy may arise. Moreover, since blast cells in acute lymphoblastic leukaemia do not express functional immunoglobulin, we infer that the tumor cell-associated VH family repertoire is determined through antigen-independent mechanisms.