Heat shock proteins are potent regulators of apoptosis, and so they may also be involved in normal cellular differentiation and cancerogenesis. We used quantitative two-dimensional gel electrophoresis for determining whether either the constitutive chaperonic heat shock cognate protein 70 (hsc70) or heat shock protein 60 (hsp60) contribute to B-cell differentiation and leukemogenesis. We compared the expression of these hsps in normal peripheral blood (PB) CD19+ B-cells, in pediatric bone marrow (BM) CD19+ CD10+ B-cell precursors (BCPs) from normal donors, and in BCPs from common acute lymphoblastic leukemia (c-ALL) patients at diagnosis and at relapse. We found that the mean levels of hsc70 in c-ALL BCPs at initial presentation and at relapse failed to differ significantly. Likewise, they failed to differ significantly from the level in high-expressing normal BM BCPs or from that in low-expressing PB B-cells. Mean levels of hsp60 expression in c-ALL BCPs at initial presentation and at relapse were similar and not distinguishable from that in normal BM BCPs, however, elevated (by a factor of 2-3) compared with that in PB B-cells. Hsc70 and Hsp60 expressions were increased (by a factor of 2 of mean levels) in populations of normal BM BCPs as compared with populations of PB B-cells. Thus, no abnormal levels of hsc70 and hsp60 were detectable in populations of pediatric c-ALL BCPs neither at diagnosis nor at relapse. In contrast, our data were in support of developmentally regulated levels of hsc70 and hsp60 expression during B-cell ontogenesis.