SUMMARY Objective: Review the results of assessing cerebral vasospasm after subarachnoid hemorrhage using transcranial doppler ultrasound. Subjects and methods: A retrospective, cross-sectional descriptive study was performed on 39 patients with subarachnoid hemorrhage treated at the Neurology Center, Bach Mai Hospital from January 2020 to September 2023. Results: The mean age of the study group was 55.12 ± 14.33. The age group distribution with the highest incidence is 41-50 years old with a rate of 35.9%. The male/female ratio is 20/19. The most common symptoms were headache (97.4%), nausea and vomiting (92.3%), The least common symptoms were convulsions and hemiplegia in 5.1% of subjects. The most common clinical severity assessed by the Hunt and Hess scale is level 2 (59%), followed by level 3 (23.1%), level 4 (10.2%), and level 1 (5.1%). Evaluation of Fisher scale found that the most common fisher level is level 4 with a rate of 33.6%, followed by level 3 (28.2%), level 1 (25.6%), the least common is grade 2 with 2.6%. The results of the second transcranial Doppler ultrasound performed on the sixth to eighth day of the disease is the time with the highest rate of vasospasm, showing the most vasospasm cerebral artery is the middle cerebral artery: right middle cerebral artery. 35.9%, left middle cerebral artery 12.8%. Next is anterior cerebral artery spasm: right anterior cerebral artery 23.1%, left anterior cerebral artery 2.6%. Right posterior cerebral artery 10.3%, left posterior cerebral artery 5.1%. Compared to the gold standard for diagnosing vasospasm, which is 128-slices MSCT, transcranial Doppler ultrasound has a sensitivity of 0.91, a specificity of 0.88, a positive predictive value of 0.91, and a negative predictive value of 0.88. The appropriateness of transcranial Doppler ultrasound and 128-slices computed tomography scan in diagnosing cerebral vasospasm after subarachnoid hemorrhage is very high, Kappa coefficient = 0.791, statistically significant with p < 0.05. Conclusion: Clinical symptoms of the disease are very diverse and non-specific, the most common symptom being headache is 97.4%. The most common Hunt and Hess scale to assess clinical severity is 2, however the most common Fisher scale is 4. Middle cerebral artery thrombosis has the highest rate of spasm, followed by the anterior cerebral artery. Compared to the gold standard for diagnosing vasospasm, which is 128-slices MSCT, transcranial Doppler ultrasound has a sensitivity of 0.91, a specificity of 0.88, a positive predictive value of 0.91, and a negative predictive value of 0.88