We have previously shown that αB‐crystallin is a heat‐shock protein which specifically accumulates in response to the expression of c‐Ha‐ras and v‐mos oncogenes in mouse NIH 3T3 fibroblasts. Elevated levels of αB‐crystallin mRNA or protein were shown to be associated with pathological conditions of the brain. Therefore, we have examined the expression of αB‐crystallin in normal human brains and brain tumors by Western blot analysis. αB‐crystallin is moderately expressed in adult but not fetal brain. Elevated levels of αB‐crystallin expression are observed in glial tumors such as astrocytoma, glioblastoma multiforme, and oligodendroglioma. αB‐crystallin in these tumors is predominately unphosphorylated. High amounts of accumulated aB‐crystallin in astrocytic tumors are preferentially found in the more aggressive stages. Glioblastoma multiforme is exceptional in that high αB‐crystallin expression is observed in only one half of the analyzed samples whereas no aB‐crystallin could be detected in the other. These results indicate that αB‐crystallin may be a useful biochemical marker for studying the pathogenesis of various human brain tumors.