<h3>Objective:</h3> To describe the characteristics and risk factors of patients who suffered strokes after radiation therapy for primary brain tumors. <h3>Background:</h3> Strokes can complicate the treatment of individuals with primary brain tumors due to several possible mechanisms including chemotherapy and radiation-induced toxicity as well as disease-specific etiologies. Little is known about the prevalence and risk factors of stroke in this population. <h3>Design/Methods:</h3> This is a retrospective cohort from a single tertiary academic brain tumor center of patients with primary brain tumors who also received radiation therapy. We report on the prevalence and types of strokes following brain tumor diagnosis and compare the risk factors among those with or without stroke. <h3>Results:</h3> We identified 443 patients with primary brain tumors who had received radiation therapy. 63 patients (14.2%), with 52.4% male and 47.6% female, mean age 57.46 (SD 12.46), were found to have suffered a stroke, 40 being ischemic (63.5%) and 23 hemorrhagic (36.5%), during their treatment course. Patients who had a stroke were more likely to have hyperlipidemia (66.7% vs. 30.6%, OR 4.91, 95% CI 2.78–8.67, P<0.0001), diabetes mellitus (17.5% vs. 8.4%, OR 2.68, 9%% CI 2.67–5.67, P=0.01), hypertension (57.6% vs. 49.6%, OR 1.51, 95% CI 0.88–2.59, P=0.13), and obstructive sleep apnea (9.5% vs. 4.7%, OR 2.25, 95% CI 0.85–5.94, P=0.10). In the patients with stroke, 65.1% were on bevacizumab at the time of the stroke. Of the 62 patients with stroke in known locations, 82% had strokes on the same side as radiation with 53% having strokes in the same location of radiation therapy. <h3>Conclusions:</h3> Patients with primary brain tumors undergoing radiation therapy who were diagnosed with stroke had higher rates of comorbid vascular risk factors, with statistically significantly higher odds of hyperlipidemia and diabetes and more often had strokes on the same side and location as their radiation therapy. <b>Disclosure:</b> Dr. Ryan has nothing to disclose. Dr. Sugita has nothing to disclose. Eric Lipp, 10512 has nothing to disclose. Dr. El Husseini has nothing to disclose. Dr. Peters has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for Vivacitas Oncology. Dr. Peters has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Servier. Dr. Peters has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Sapience. Dr. Peters has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for NuVox Therapeutics. Dr. Peters has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for Cordance Medical. Dr. Peters has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for ONO Pharmaceutical. Dr. Peters has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Blue Earth Diagnostics. The institution of Dr. Peters has received research support from Novocure. The institution of Dr. Peters has received research support from Biomimetix. The institution of Dr. Peters has received research support from Servier. The institution of Dr. Peters has received research support from Varian. The institution of Dr. Peters has received research support from Sapience. Dr. Peters has received personal compensation in the range of $500-$4,999 for serving as a Educational Lecturer with Eisai.