Bronchopulmonary infections caused by trichomonads have been reported principally in patients with pre-existing pulmonary diseases, such as bronchial carcinoma, lung abscess, or bronchiectasis. Pulmonary trichomoniasis is most often caused by Trichomonas tenax, which is usually regarded as a harmless commensal organism of the human mouth. However, pulmonary infection may rarely be caused by other trichomonas species, including Trichomonas vaginalis from the genitourinary tract and Trichomonas hominis from the intestines. Because of the rarity of trichomonas pulmonary infection, and because of its close association with underlying lung and systemic disease, pulmonary trichomoniasis is considered an opportunistic infection. We recently treated a case of pulmonary trichomoniasis occurring in a young, healthy male without obvious underlying pulmonary or systemic illness. To our knowledge, there has been only one reported case of pulmonary trichomoniasis in Korea, and there have been only two reported cases of pulmonary trichomoniasis occurring in normal lung worldwide.