Six chemical agents were evaluated for their efficacy in preventing epidural scar formation following laminectomy in rabbits. One agent was carboxymethylcellulose and the other five agents represented various compositions of modified carboxymethylcellulose. Four weeks after laminectomy, spines were harvested and decalcified, and transverse sections were prepared for histologic analysis. Subjective evaluation suggested that two agents appeared to inhibit epidural scar formation compared with the untreated controls. Objective evaluation was performed by quantitating scar tissue area at the laminectomy site with a digitizing tablet. In agreement with the subjective evaluation, two agents were found to have significantly reduced epidural scar tissue area compared with the control (control = 0.418 +/- 0.16 SE mm2vs. Agent 2 = 0.067 +/- 0.02 [P less than 0.05] and Agent 5 = 0.089 +/- 0.02 [P less than 0.05]). Of the remaining four agents, one of which was the unmodified carboxymethylcellulose, none showed significant reduction in scar tissue formation. These findings indicate that viscous preparations of modified carboxymethylcellulose can act as a barrier against epidural scar formation following laminectomy.