Background & aims: Antioxidant status is disturbed in asthma. Measurement of both oxidized and reduced forms of antioxidants provides important information regarding the oxidant/antioxidant balance. The aim of this study was to investigate the clinical relevance of key antioxidants (α-tocopherol and glutathione) in asthma, by measuring the oxidized and reduced forms, in the airways (induced sputum) and systemically (peripheral blood). Methods: This cross-sectional study examines stable asthmatics (n=44) and healthy controls (n=31) recruited through John Hunter Hospital, NSW, Australia. We collected peripheral blood and induced sputum during hypertonic saline challenge. α-tocopherol and α-tocopherol quinone were measured by HPLC. Total glutathione and glutathione disulfide were determined by a colorimetric assay. Results: Plasma α-tocopherol was low in asthma versus controls. Subjects with asthma had higher levels of whole blood α-tocopherol quinone and %α-tocopherol quinone than controls and %α-tocopherol quinone correlated with asthma control (p=0.009). Sputum supernatant levels of total, reduced and oxidized glutathione were elevated in asthma versus controls. Oxidized glutathione in sputum supernatant negatively correlated with FEV₁/FVC% (p=0.029).