en Basic Neurosurgery Research <strong>Background and Aim:</strong> Chronic subdural hematomas (CSDH) are a common neurosurgical issue characterized by the accumulation of blood between the brain and its outermost protective membrane. The pathogenesis of CSDH involves a cycle of recurrent hemorrhage, fibrinolysis, inflammation, and angiogenesis. D-dimer, a marker of fibrinolysis, has been investigated in CSDH. This study explores the correlation between D-dimer levels, computed tomography (CT) findings, and recurrence of CSDH.<br> <strong>Methods and Materials/Patients:</strong> This prospective study included 80 patients with CSDH who underwent surgical evacuation between 2018 and 2020. The CSDHs were classified based on CT scan appearance, and D-dimer levels were measured in the hematoma fluid and peripheral blood samples. The statistical analysis was performed to identify correlations between D-dimer levels, CT subtypes, and recurrence rates.<br> <strong>Results: </strong>The mean D-dimer value in the Hypodense group was 454.2 mg/L while the value in the isodense group was 777.74 mg/L. The highest mean value was observed in the mixed subgroup, at 2370 mg/L. The layered group had a mean value of 1146.85 mg/L. The mean D-dimer value in the homogenous group was 622.48 mg/L while the mean in the heterogenous group was 2014.57 mg/L. There was a statistically significant correlation between the imaging subtypes and the D-dimer values (P=0.01).<br> <strong>Conclusion:</strong> The mean D-dimer values were highest in the mixed subtype of CSDH, followed by the layered subtype, while the hypo- and isodense subtypes had lower D-dimer levels. There was a significant correlation between the imaging subtypes and D-dimer values. Additionally, a higher rate of recurrence was observed in the mixed subtype group, which also had higher D-dimer values. Steroid administration after surgery showed a statistically significant negative correlation with recurrence rates. D-DIMER, CHRONIC SUB DURAL HEMATOMA, RECURRENCE 0 0 http://irjns.org/browse.php?a_code=A-10-730-1&slc_lang=en&sid=1 Sangeetha Adhikesavan 100319475328460012283 100319475328460012283 No Sri Ramachandra Medical College and Research Institute, Chennai, India. Visvanathan Krishnaswamy visvanathan.k@sriramachandra.edu.in 100319475328460012284 100319475328460012284 No Sri Ramachandra Medical College and Research Institute, Chennai, India. Sai Sriram Swamiyappan saisriramswamiyappan@gmail.com 100319475328460012285 100319475328460012285 Yes Sri Ramachandra Medical College and Research Institute, Chennai, India. Vivek Visvesvaran 100319475328460012286 100319475328460012286 No Sri Ramachandra Medical College and Research Institute, Chennai, India. Balasubramanian Kannan 100319475328460012287 100319475328460012287 No Sri Ramachandra Medical College and Research Institute, Chennai, India.