We describe a case of desquamative interstitial pneumonia diagnosed in a 25-year-old woman who relapsed 12 times during a 20-year follow-up period. In each relapse, the involved sites were different and the patient ultimately recovered without resultant pulmonary ventilatory defects. Bronchoalveolar lavage performed during the 12th relapse revealed a remarkable increase in the number of total cells and showed a low CD4+/CD8+ ratio in the lymphocyte subset.