Aging process involves an increase in stress at cellular level. We studied whether aging affects the regulation of stress responsive transcription factor NF-κB in brain samples of Wistar rats. Hippocampus, cerebellum, and temporal and frontal lobes of cortex were studied. We observed a significant up-regulation in the constitutive, nucleus-located NF-κB binding activity in 30-month-old Wistar rats compared to young and 18-month-old rats. The increase was most prominent in cerebellum and in frontal cortex, but age-related changes did not occur in hippocampus. Inducible, cytoplasmic NF-κB binding activity was not affected by aging in any of the samples studied. Western blot assays did not show any age-related changes in the nuclear level of p50, p52, and p65 protein components of NF-κB complex. Cytoplasmic level of inhibitory IκB-α was also unaffected. The increase in nuclear constitutive NF-κB binding activity during aging may be related to the NF-κB driven cellular response to adapt neurons against apoptotic pressure, as observed recently in several apoptotic conditions.