Background: The importance of invasive pulmonary aspergillosis (IPA) in patients with haematological malignancy or solid organ transplantation has been highlighted, but IPA has been neglected in the patients with nasopharyngeal cancer (NPC). Case 1: A 58-year-old woman of NPC had fever and cough due to right lung consolidative pneumonia. Initial laboratory data showed WBC 300/mL, platelet count 77000/mL, procalcitonin 26.64ng/ml, CRP 310.3mg/L, lactic acid 4.2mmole/L, and albumin 2.2g/dL. Sputum culture yielded Pseudomo- nas aeruginosa and yeast-like organisms. Blood Aspergillus antigen index revealed 0.38 and 0.11 twice. Antibiotics with imipenem and levofloxacin did not achieve improvement. Then BAL Aspergillus antigen revealed 0.54 (40.5, positive). Voriconazole was added, but pneumonia was getting worse. Although with intensive care, patient died after 30 days of hospital stay. Case 2: A 51-year-old man of NPC had fever, cough and dyspnea due to bilateral interstitial pneumonia. Laboratory data showed WBC 10400/mL, band form 12%, platelet 341000/mL, CRP 470.5mg/L, lactic acid 1.6mmole/L, and albumin 4.2g/dL. Sputum culture yielded mixed normal flora. Blood Aspergillus antigen index revealed 47.84 (positive). Chest CT showed reticular micro- nodules and interstitial infiltration over both lungs. Piperacillin/tazobactam, levofloxacin and voriconazole achieved improvement. Two weeks later, blood Aspergillus antigen index became 3.69. He was discharged after 22 hospita- lized days with oral voriconazole for maintenance therapy. Case 3: A 70-year-old man of NPC had frequent chocking episodes, cough and high fever, suspected of aspiration pneumonia. Laboratory data showed WBC 7,200/mL, platelet 208000/mL, procalcitonin 4.41ng/ml, CRP 145.8mg/L, lactic acid 1.2mmole/L, and albumin 0.7g/dL. Blood culture yielded Enterococcus faecalis. Sputum culture yielded mixed flora. Amox- icillin/clavunanic acid was used but was changed to piperacillin/tazo- bactam as worsening pneumonia by Klebsiella pneumoniae and septic shock developed. Blood Aspergillus antigen index revealed 0.74 (positive), but voriconazole was not administered as improved condition. The patient was discharged after 19 days of hospital stay with residual inter- stitial process over bilateral lungs. Conclusions: In conclusion, we reported on 3 NPC patients with IPA- related worsening pneumonia. Blood Aspergillus antigen was positive during early course in 2 patients, but was negative in one patient who showed positive BAL Aspergillus antigen in the late course. IPA should be considered early in the NPC patients with pneumonia.