BACKGROUND The role of glucocorticoids without surgical evacuation in the treatment of chronic subdural hematoma is unclear. METHODS In this multicenter, open-label, controlled, noninferiority trial, we randomly assigned symptomatic patients with chronic subdural hematoma in a 1:1 ratio to a 19-day tapering course of dexamethasone or to burr-hole drainage. The primary end point was the functional outcome at 3 months after randomization, as assessed by the score on the modified Rankin scale (range, 0 [no symptoms] to 6 [death]). Noninferiority was defined by a lower limit of the 95% confidence interval of the odds ratio for a better functional outcome with dexamethasone than with surgery of 0.9 or more. Secondary end points included scores on the Markwalder Grading Scale of symptom severity and on the Extended Glasgow Outcome Scale. RESULTS From September 2016 through February 2021, we enrolled 252 patients of a planned sample size of 420; 127 were assigned to the dexamethasone group and 125 to the surgery group. The mean age of the patients was 74 years, and 77% were men. The trial was terminated early by the data and safety monitoring board owing to safety and outcome concerns in the dexamethasone group. The adjusted common odds ratio for a lower (better) score on the modified Rankin scale at 3 months with dexamethasone than with surgery was 0.55 (95% confidence interval, 0.34 to 0.90), which failed to show noninferiority of dexamethasone. The scores on the Markwalder Grading Scale and Extended Glasgow Outcome Scale were generally supportive of the results of the primary analysis. Complications occurred in 59% of the patients in the dexamethasone group and 32% of those in the surgery group, and additional surgery was performed in 55% and 6%, respectively. CONCLUSIONS In a trial that involved patients with chronic subdural hematoma and that was stopped early, dexamethasone treatment was not found to be noninferior to burr-hole drainage with respect to functional outcomes and was associated with more complications and a greater likelihood of later surgery. (Funded by the Netherlands Organization for Health Research and Development and others; DECSA EudraCT number, 2015-001563-39.).