Reactive oxygen intermediates (ROIs) are involved in many neurological diseases. Despite the toxic nature of these compounds, low concentrations of ROIs can function as signaling molecules. One target for their signaling function is the inducible transcription factor NF-kappa B. Predominantly in lymphoid cells, induction of NF-kappa B in response to oxidative stress leads to transcriptional activation of many genes which are relevant for pathogen defense. These include the TNF, IL-6, IL-8, GM-CSF, beta-interferon, MHC class I and V-CAM genes. However, NF-kappa B is also abundant in various cell types of the nervous system, including neurons. We propose that NF-kappa B plays a role as a redox-controlled transcriptional activator also in cells of the nervous system and in that property may contribute to neurological disorders. Our finding that some neurons from healthy brain contain constitutively active NF-kappa B suggests a role of NF-kappa B in normal brain function as well.