Background: Ciliary neurotrophic factor (CNTF), identified as a survival factor for developing peripheral neurons is upregulated by reactive astrocytes in the traumatized tissue and in areas of terminal degeneration after a brain lesion. But in the spinal cord, CNTF is expressed in the non-astrocytic phenotypic, maybe oligodendrocytes. The present study was undertaken to determine the upregulation of CNTF expression in reactive astrocytes following spinal cord lesion in the rat. Methods: Unilateral incision of the dorsal funiculus at the thoracic level was performed and rats were sacrificed on days 3, 7, 14 and 28 postlesion. Western blot analysis, immunocytochemical analysis and double immunofluorescence for CNTF and glial fibrillary acidic protein (GFAP) were performed after spinal cord lesion. Results: A major band with 24 kDa and additional band of higher molecular weight form were detectable, and the intensity of the 24 kDa immunoreactive band increased up to 14 days postlesion and decreased toward laminectomized control values. CNTF immunoreactivity was markedly upregulated in the injured dorsal funiculus and adjacent gray matter. The time course of CNTF expression is coincident with the appearance of reactive astrocytes in the injured spinal cord. Moreover, double immunofluorescence for CNTF and glial fibrillary acidic protein (GFAP) revealed that CNTF immunoreactivity was in GFAP immunoreactive astrocytes. Conclusions: These results show that CNTF upregulation occurred in reactive astrocytes following spinal cord lesion, and suggest a role for CNTF in the regulation of astrocytic responses after spinal cord injury.