Strongyloidiasis is widely distributed in tropical and subtropical areas. Disseminated strongyloidiasis may develop in patients with immunodeficiencies. In the absence of early diagnosis and treatment, the prognosis of disseminated strongyloidiasis is extremely poor. We report a case of pulmonary strongyloidiasis that was successfully treated. The patient was an 83-year-old woman who had been receiving long-term oral prednisolone therapy for uveitis. The patient visited our emergency department complaining of breathing difficulties and diarrhea. A chest X-ray revealed a diffuse enhancement of interstitial shadows. A bronchoalveolar lavage (BAL) was performed, and both Gram staining and Grocott's staining revealed the presence of multiple filariform larvae of Strongyloides stercoralis in the bronchoalveolar lavage fluid (BALF). A stool examination performed at the same time also yielded S. stercoralis. The patient was diagnosed as having pulmonary strongyloidiasis and was treated with thiabendazole and ivermectin, in addition to antimicrobial agents; her respiratory symptoms and diarrhea improved, and S. stercoralis was not detected in subsequent follow-up examinations thereafter. In endemic areas of S. stercoralis, pulmonary strongyloidiasis should be considered as part of a differential diagnosis if chest imaging findings like alveolar and interstitial shadow patterns or lobar pneumonia are seen in patients with immunodeficiencies. (Internal Medicine 43: 731-736, 2004)