Idiopathic pulmonary fibrosis (IPF) is a disease of unknown aetiology. Increased oxidant burden and antioxidant, e.g. glutathione (GSH), deficiency in the lower respiratory tract have been thought to play a role in the progression of IPF. Sputum induction is a safe noninvasive tool to study inflammation in the respiratory tract. The aim of the present study was to evaluate the direct measurement of GSH in induced sputum supernatant. Sixteen IPF patients and 15 healthy, nonsmoking subjects underwent sputum induction. Total GSH in sputum, saliva and plasma was measured spectrophotometrically. Sputum GSH was decreased more then four-fold in IPF patients when compared to healthy subjects (mean GSH 1.4+/-0.34 microM versus 5.8+/-0.98 microM). Salivary GSH was generally low or undetectable in all subjects. Plasma GSH levels were lower in IPF patients (0.26+/-0.1 versus 0.74+/-0.16 microM). In IPF patients, there was a borderline correlation of sputum GSH levels with disease duration and lung-function impairment. These data confirm the established role of oxidant/antioxidant imbalance in the pathogenesis of idiopathic pulmonary fibrosis, and show the potential of induced sputum to directly study inflammatory processes and surrogate markers in interstitial lung diseases like idiopathic pulmonary fibrosis.