The prognosis of patients complicated with interstitial pneumonia (IP) who undergo pulmonary operations is very poor if acute exacerbation occurs after the operation. We have experienced 6 cases in which operations were performed on lungs complicated with IP The first patient died due to acute exacerbation, but the subsequent 5 patients had good postoperative courses due to 1) short-term administration of low-dose steroid before and after the operation, 2) avoidance of administration of high concentration of oxygen during and after the operation, and 3) administration of erythromycin before and after the operation, 4) N-acetylcysteine inhalation and administration of dl-alpha-tocopherylnicotinate before and after the operation. It is thought that careful management of such patients is needed to prevent acute exacerbation even after discharge from hospital.