ABSTRACTReactive oxygen species (ROS) are known aggravating factors for airway inflammation in asthma. Glutathione S-transferases (GSTs) detoxify ROS and toxic compounds in environmental exposures. However, little is known about the regulation of GST and expression of GST subtypes in asthma. The aim of this study was to evaluate how GSTs are regulated in asthma. We observed total GST activity and expression of GST subtypes in murine asthma models and GST expressions in induced sputum cells of asthmatics. Total GST activity was increased in BAL fluids of OVA-treated murine asthma model. GSTP and GSTA are highly expressed in peribronchiolar mononuclear inflammatory cells and epithelial cells in OVA-treated mice. GSTM are expressed in epithelial cells in both OVA and PBS-treated groups. GSTP1 mRNA expression was increased in the lung of OVA-treated mice compared with PBS-treated mice. GSTA1, GSTM1, and GSTT1 mRNA expressions were not different between both groups. GSTA1 mRNA expression was increased in induced sputum cells of asthmatics compared with healthy controls. GSTP1, GSTM1, and GSTT1 mRNA expressions were not different between asthmatics and healthy controls. In asthmatics, GSTP1 and GSTA1 mRNA expressions were higher in induced sputum cells of asthmatics with PC20 ≤ 4 mg/ml than those with PC20 > 4 mg/ml. GSTM1 and GSTT1 mRNA expressions were not different between two groups. These findings suggest that GSTs are upregulated in the airways of asthmatics in response to increased oxidative stress. GSTP and GSTA are thought to play an important role in protecting the airways of asthmatics compared with GSTM and GSTT.