THE nuclear factor-kappa B (NFkB) and the signal transducer activator of transcription 3 (STAT3), are putative transcription factors activated by growth factors and cytokines, and involved in glial gene expression changes after neuronal injury. Immunocyto-chemical analysis of NFκB and STAT3 from 2 h to 14 days after excitotoxic damage to the postnatal rat brain showed STAT3-and NFkB-positive glial cells at 2 h post-lesion, increasing in number to reach a maximum at day 1. Immunoreactivity then decreased but the glial scar remained positive. Glial STAT3 immunoreactivity was located in the nucleus up to 1 day post-lesion and in the nucleus, cytoplasm and cell processes from day 3. Glial NFκB immunoreactivity was mainly cytoplasmatic.