ABSTRACT—This study investigates the effects of N‐acetylcysteine (NAC) and rutin on the lung oxidative burden of patients with early adult respiratory distress syndrome (ARDS). The protection was evaluated by measuring expired ethane and malondialdehyde (MDA), and oxidized (GSSG) and reduced glutathione (GSH) in the epithelial lining fluid of 36 patients who developed ARDS less than 24 hours before enrollment in the study. The patients were randomly assigned to 3 groups, receiving 250 mL 5% dextrose in water (group 1), NAC 50 mg/kg body weight in 5% dextrose (group 2), and NAC 50 mg/kg + rutin 5 mg/kg in 5% dextrose (group 3). Ethane and MDA concentrations were significantly reduced in the treatment groups after day 6. GSH was 30% increased in the treatment groups. No significant variations were observed in the control group until day 9. The trial confirms that NAC and rutin are efficient in protecting the lungs of patients with ARDS.