BACKGROUND: Stroke is a disease that leads to a long period of disability and death. Accordingly, the initial treatment is so influential on the prognosis of a patient that shortening the time to initial treatment after hospital admission has a very important role in the entire treatment regimen. This study aimed to demonstrate the effect of the Emergency Department treatment time at Bundang CHA Hospital for acute stroke patients to improve the treatment regimen through six sigma activities. METHODS: The outcomes for 246 patients with suspected acute strokes who were admitted to the Emergency Department of Bundang CHA Hospital, the flow of the emergency department process divided into 11 phases, and the duration of each phase were determined. Patients were classified as before and after six sigma activities and compared. RESULTS: The five phases statistically demonstrated the effect of meaningful improvement in the duration of visit-receiving CT prescriptions, visit-receiving lab prescriptions, consult request-arriving to the emergency department, visit-CT angiography results, and visit-the issue of hospital admissions. In the next 2 phases, the sigma level also improved by 0.71sigma and 0.06sigma. However, the total emergency department stay time was not statistically meaningful. The time required time was increased and the sigma level was decreased by 0.19sigma. CONCLUSIONS: The result of six sigma activities showed the effect of the treatment system improvement with a partial decrease in the duration of each phase, but the total emergency department stay time was not improved owing to environmental factors. For better results, continuous improvement of the treatment system and expansion of hospital facilities will be required.