Sulfhydryl groups (SH) are considered a key factor in redox sensitive reaction of plasma, and their modification could be considered an expression of abnormal generation of oxygen free radicals. METHODS: Fifty consecutive patients with acute brain stroke were enclosed in this study. The plasma concentrations of SH groups were correlated to cytokines (IL-1b, IL-6, IL-8, TNF- α ), plasma chitotriosidase (Chit), metalloprotease (MMP2-9), intercellular adhesion molecule-1 (ICAM-1). RESULTS: The results demonstrated a significant reduction of SH groups within 24 hours from the onset of an acute ischemic stroke, a reduction of plasma IL-1b, IL-6, and IL-8, and an increase of Chit and TNF- α in relation to the stroke severity. CONCLUSION: The observation of an intense microenvironment activation that follows the stroke and the correlation between SH levels and markers of immune response suggest that, especially in stroke, is necessary to maintain the redox function to prevent the brain damage. The reduced SH levels represent an attempt to neutralize the abnormal generation of free radicals. Since the reperfusion of brain after ischemic event represents a severe oxidative stress, which must be corrected by regeneration of redox sensitive function, pharmacological intervention could be beneficial in this setting.