The present study was designed to evaluate inflammatory changes in collapsed lungs during one-lung ventilation using the assistance of a bronchoscopic microsampling probe. Serial albumin and interleukin (IL)-8 concentrations in epithelial lining fluid (ELF) were measured in seven patients undergoing resection of lung tumors. The samples were taken after induction of anesthesia (baseline), 30 min after one-lung ventilation was started (point 2), just before resuming two-lung ventilation (point 3), and 30 min after two-lung ventilation was restarted (point 4). The albumin and IL-8 concentrations in ELF were significantly increased at point 2 and point 3, respectively, and remained to be high, compared to the baseline. The increase in IL-8 at point 3 was correlated with the interval of one-lung ventilation; however, none developed specific acute lung injury. These findings suggest that inflammatory changes can occur on the epithelium of a collapsed lung even in patients who underwent successful and standard thoracic surgery.