A 74-year-old woman was admitted to our hospital because of interstitial pneumonia. She had a 14-year history of primary biliary cirrhosis (PBC) diagnosed histologically, with a positive test for anti-mitochondrial antibodies and elevated biliary enzyme activity. She also had a 7-year history of rheumatoid arthritis and a 26-year history of Sjögren's syndrome. Though the symptoms of these complications improved, the interstitial pneumonia deteriorated very quickly and the patient died of respiratory failure due to acute exacerbation of interstitial pneumonia when the activity of PBC decreased. We report this case because it is relatively rare for PBC to be complicated by severe interstitial pneumonia, and it may offer insight into the etiology of these diseases.