To examine whether spinal cord decompression improves functional recovery and decreases lesion volumes in paraplegic (not paraparetic) rats and, if so, at what postoperative time it is most efficacious. The spinal cords of 63 female rats were compressed at T9 with Yasargil clips. Rats were assigned randomly to five different treatment groups of 3 s, 1 hr, 6 hr, 3 weeks, and 10 weeks. Locomotor behavior scoring was based on the Basso, Beattie, Bresnahan (BBB) Locomotor Rating Scale (Ohio State University, Columbus, OH) motor scores. Comparing five groups, the mean BBB was statistically higher in the 3-s group (P < 0.05). Comparison of progressive changes in BBB in each group revealed statistically meaningful improvement in the 3-s group, too. Spared surface area of spinal cord was 81.5 +/- 4.9% in 3-s group and 10.8 +/- 1.4% in the delayed groups of decompression (P = 0.039). Rats undergoing immediate decompression showed significantly better functional recovery and smaller lesion volumes.