Twocases of acute eosinophilic pneumoniafollowing cigarette smoking are analyzed for characteristic features. The first patient noted dyspnea 14 days after initiation of smoking. The second patient noted dyspnea 12 days after beginning to smoke. Both cases had characteristic features including occurrence at an age younger than 30 years; less than 1 month duration of cigarette smoking before onset of disease ; and no identifiable cause of acute eosinophilic pneumoniaapart from smoking. Webelieve that acute eosinophilic pneumonia following cigarette smoking, which has characteristic features as described above, should be considered as a distinct subtype of AEP. (Internal Medicine 39: 830-833, 2000)