['This study investigated the relationship between traumatic coagulopathy and severe brain swelling (SBS) during decompressive surgery to evacuate a supratentorial intradural mass lesion in patients with traumatic brain injury (TBI).', 'A retrospective study was conducted in 96 patients who consecutively suffered from isolated TBI and underwent decompressive surgery to evacuate a supratentorial traumatic mass lesion by unilateral craniotomy. Their medical history, radiographic information, and surgical notes were reviewed. The relationship between traumatic coagulopathy and intraoperative SBS was evaluated.', 'Fifty-six patients presented with traumatic coagulopathy according to their preoperative coagulation panels. Thirty of them had the disorder corrected before surgery while the remaining patients did not. Twenty-four patients developed intraoperative SBS, and 22 (91.7%) of them were related to new or progressive formation of distal intracranial lesions during the surgery. Patients with uncorrected coagulopathy demonstrated a significantly higher risk of intraoperative SBS than those with corrected and no coagulopathy (61.5% vs 11.4%, P < 0.001). There was no significant difference in the incidence of intraoperative SBS between patients with corrected and no coagulopathy (13.3% versus 10.0%, P > 0.05). Multivariate logistic regression analysis showed that uncorrected coagulopathy was an independent risk factor and related to an 11.5-fold increased risk of intraoperative SBS.'] Is uncorrected traumatic coagulopathy associated with severe brain swelling during decompressive surgery to evacuate a supratentorial intradural mass lesion in patients with traumatic brain injury?