Multicentric Castleman's disease (MCD) is a rare polyclonal lymphoproliferative disorder that manifests with lymphadenopathy and inflammatory symptoms. In order to clarify the clinical features and actual management of MCD in Japan, we analyzed 21 patients diagnosed with MCD and treated in Kyoto University Hospital between 2005 and 2012. There were 12 men and 9 women. The median age at disease onset was 46 years, and the median follow-up period was 98 months. Common symptoms included splenomegaly (13/20), renal dysfunction (11/21), interstitial pneumonia (7/21), pleural effusion and/or ascites (7/21), and thrombocytopenia (6/21). The results of the anti-human immunodeficiency virus antibody and human herpes virus-8 DNA tests in the blood were available in 13 and 5 cases, respectively, and no patient was positive for either. Among 12 patients treated with tocilizumab, an anti-interleukin-6 receptor antibody, 11 exhibited an improvement in MCD-related symptoms and 3 achieved complete resolution of all these symptoms. In 8 patients treated with tocilizumab for over 1 year, the mean Hb level increased from 7.4 to 12.2 g/dL while the mean serum C-reactive protein level decreased from 13.2 to 0.4 mg/dL. Three patients died during the observation period due to sepsis, secondary leukemia, or pancreatic cancer. The clinical courses of most cases were indolent; however, in some cases with pleural effusion, ascites, renal dysfunction, and/or thrombocytopenia, the disease manifestation was serious. A nationwide survey is required to further clarify the epidemiology, clinical features, and optimal treatment strategies of MCD in Japan.