The effect of polymixin B-immobilized fiber column (PMX) hemoperfusion treatment for acute exacerbation of interstitial pneumonia (IP) has been reported. Here, we report 2 cases of acute exacerbation of IP successfully treated with PMX hemoperfusion. One is a 55-year-old woman who was diagnosed as microscopic polyangiitis (MPA) with IP. The other is a 58-year-old man, diagnosed as having idiopathic pulmonary fibrosis. Both cases were treated with PMX hemoperfusion and other therapies. One died on day 44 and the other is still alive. The PMX hemoperfusion treatment decreased the serum levels of several cytokines and activated neutrophil percentage in bronchoalveolar lavage fluid.