The aim of current study was to analyze the binding activity and the temporal and cellular expression of nuclear factor kappa B (NF-kappaB) in human contused brain. Eighteen contused brain samples were obtained from 17 patients undergoing surgery for brain contusions 5-80 h after trauma. NF-kappaB binding activity was detected by electrophoretic mobility shift assay (EMSA), and temporal and cellular expression of NF-kappaB subunits p65 and p50 was analyzed by immunohistochemistry. The results showed that a progressive upregulation of NF-kappaB activity occurred in the area surrounding the injured brain with the time from brain trauma to operation. The maximal expression of NF-kappaB was detected after 48 h postinjury. The expression of NF-kappaB p65 was mainly located at glial and vascular endothelial cells without expression at neurons. The expression of NF-kappaB p50 was mainly located at glial cells, a little at neurons and no expression at vascular endothelial cells. Within 24 h postinjury, both NF-kappaB p65 and p50 immunoreactivity was mainly observed in the nucleus of cells. After 24 h postinjury, NF-kappaB p65 labeling was found in the both nucleus and cytoplasm of glial and endothelial cells; otherwise, p50 labeling was primarily found in the nucleus of glial cells and in the nucleus, cytoplasm and process of neurons. It is concluded that NF-kappaB could be highly upregulated at human contused brain and the cellular pattern of p65 and p50 expression might be closely associated with the cell functions.