77 patients with epidural hematoma were randomized to undergo posterior lumbar decompression and instrumented fusion with either a large diameter suction drain or a small diameter suction drain. The object of this study was to determine if a larger diameter suction drain would reduce the amount of postoperative epidural hematoma. Findings indicated no significant differences between drain sizes with regards to the size of remaining hematomas measured by the degree of thecal sac compression. Additionally, there were no differences in prothrombin time, activated partial thromboplastin time, platelet number blood loss, or operation duration. However, platelet function analysis was significantly shorter in duration in the larger diameter group compared to the shorter diameter group.