Objective To explore the cell proliferation and survival in the spinal cord of adult ALS transgenic mice. Methods BrdU was injected at different time points,and frozen sections were made.The cell proliferation,distribution and survival in the spinal cords were detected by immunofluorescence labeling technology. Results In ALS transgenic mice,BrdU positive cells were detected in the central canal, gray matter and white matter of the adult spinal cord, which were often found in pairs of cells of a similar size and shape. Within the gray matter,most of these cells were located in the ventral horn. In the white matter, BrdU positive cells were more diffused. There were more BrdU positive cells in ALS transgenic mice than in the wildtype mice. BrdU positive cells were detected both on the 1st and 14th day after BrdU injection, but the changes in the number was decreased.There were a few positive cells detected mainly in the central canal on the 28th day.Proliferating_cell nuclear antigen (PCNA) staining paralled the locations and characteristics of BrdU staining. For 95dayold mice (1 day after the last BrdU injection),there were more Nestin positive cells in the spinal cord of ALS transgenic mice than in the wildtype mice.Most Nestin positive cells were located in the ventral horn,and BrdU incorporation colocalized in some cells with Nestin expression. No BrdUpositive/Nestinpositive cells were detected when spinal cords were evaluated 14 or 28 days after BrdU injections.Conclusion There is a significant cell proliferation in response to neurod