Inclusion Criteria:  Consecutive subjects between ages 18 years or older evaluated in the emergency department at Harbor-UCLA Medical Center with signs and symptoms of acute ischemic stroke presenting within 24 hours of symptom onset. All individuals regardless of gender or race will be included. For adults who cannot consent for themselves because of the severity of their stroke, one of the investigators will offer participation in the study to the family member who possesses the authority for medical decision making for the patient. There is no financial incentive for either the patient or the investigator. It will also be explained that the potential benefit of giving N-acetylcysteine is unknown and that the patient will receive excellent care (standard for their presentation) whether they participate or not and outside of not receiving the study drug.  Our patients tend to be economically disadvantaged but since there are no financial incentives either for the patient or for the investigators, this bias has been minimized. Patients will receive the same care whether they participate in the study or decline.  Exclusion Criteria:  Evidence of hemorrhagic stroke on initial CT scan Need for thrombectomy as determined by the treating neurologist -Known allergy to NAC Protected populations, including age < 18, known pregnancy, and prisoners Patients who are DNR/DNI at the time of presentation with a short life expectancy