Background Previous studies have showed that photooxidative stress can lead to down-modulation of nuclear factor-κappa B (NF-κB) activity causing apoptosis of cultured photoreceptor cells. This study aimed at investigating whether NF-κB was involved in photoreceptor cells apoptosis induced by N-methyl-N-nitrosourea (MNU) in rats.Methods A single intraperitoneal injection of 60 mg/kg MNU was given to 50-day-old female rats. At different intervals after MNU treatment,the animals were sacrificed. Retinal damage was examined by a light microscope. The apoptotic index of the photoreceptor cells was detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL). NF-κB was analysed by Western blot and Transcriptin Factor Assay Kits. Results The pyknosis of the photoreceptor nuclei and the disorientation of the outer segment of the photoreceptor layer was seen after MNU treatment for 24 hours. The outer nuclear layer and photoreceptor layer were almost completely lost at 7 days. Photoreceptor cells apoptosis reached the peaked value at 24 hours. In apoptotic cascade, the protein levels of NF-κB p65 were only detected after MNU treatment for 12 and 24 hours in the nucleus. Conversely, the amounts of IκBα were markedly increased in the cytoplasm as well as in the nucleus. The activity of NF-κB p65 in the nucleus was down-modulated in the end.Conclusions MNU-induced photoreceptor cell destruction was attributed to the apoptotic process by down-regulating the activation of NF-κB p65.