A 23-year-old woman was admitted to our hospital because of cough and fever. Coarse crackles were audible over her left chest. A chest X-ray obtained on May 5, 1989, showed consolidation in the left S10 and a nodule in the right S1. Clinical symptoms improved during the course of hospitalization. Neither antibody titers against mycoplasma and chlamydia nor viral titers were elevated in paired sera. BALF findings of the left B10 showed increased numbers of eosinophils and lymphocytes. We diagnosed this case as eosinophilic pneumonia (EP). Environmental provocation testing was carried out in her home and yielded a positive result. After clearing of the house, she was able to return and has since experienced no relapses. We suspect that environmental conditions influence the pathogenesis of EP.