We report a case of drug-induced pneumonitis caused by acetaminophen taken for headache. The patient was a 49-year-old woman who had been taking a common cold drug (Benza BlockSP) containing acetaminophen and an anti-gastritis drug for headache. Seven days after she began taking acetaminophen, fever, dry cough, and dyspnea developed. The patient was admitted to our hospital on December 6,1996. Chest X-ray films and computed tomography scans revealed ground-glass and reticulonodular opacities. All chemotherapy was discontinued under a presumptive diagnosis of drug-induced pneumonitis. Transbronchial lung biopsy specimens revealed infiltration of lymphocytes and eosinophils into the alveolar walls and interstitum, with granulomotous lesions and macrophages in the alveolar spaces. The patient's chest X-ray findings improved and her symptoms subsided after the medications were stopped. However, she was given oral prednisolone (30 mg/day) because shadows were still evident on chest X-ray films. Prednisolone was effective in removing those shadows. A lymphocyte stimulation test was positive for acetaminophen. Based on the above findings, acetaminophen-induced pneumonitis was diagnosed. To our knowledge, acetaminophen-induced pneumonitis is rare. However, when drug-induced pneumonitis is suspended, common cold drugs containing acetaminophen should be kept in mind.