A 49-year-old woman was admitted to our hospital with a dry cough and bilateral hilar lymphadenopathy. She had a history of acute arthralgia and erythema nodosum 4 months before admission. Chest CT scans on admission revealed multiple mediastinal lymphadenopathy. Broncho-alveolar lavage showed CD4-dominant lymphocytosis. A biopsy specimen of the lung revealed non-caseating granuloma of epithelioid cells with giant cells, confirming the diagnosis of sarcoidosis. She recovered in one month, and has since remained well and free of the symptoms. Löfgren's syndrome is acute sarcoidosis, characterized by polyarthralgia, erythema nodosum and bilateral hilar lymphadenopathy. It is common in European countries, but very rare in Japan, from where only two case reports have appeared. This syndrome is closely related to HLA-B8, DR-3, and DR-17, but our case did not have these HLA loci. We report this case as the third case of Löfgren's syndrome in Japan.