Since our report on Castlemans lymphoma in 1958, a total of 53 cases by 36 authors have appeared in the Japanese literatures. Among them our first case, whose tumor was found in the pelvic cavity, would be the first patient ever reported in Japan. The outstanding histological features of Castleman's lymphoma consists of variegated morphology of germinal centers due to peculiar capillary proliferation, multicentric germinal centers in a lymph follicle showing a chimerical figure and expansive growth of lymph follicles by compressing interfollicular area. Among these Japanese population, we have noticed the highest age incidence between 10-19 years, with somewhat female predominance, the most preferential site in the upper part of the body, and, as compared to the other ethnical subjects, more frequent tumor multiplicity and less usual plasma cell type of the tumor. A possible pathogenesis that Castleman's lymphoma could be "a benign lymphoma" in contrast to malignant lymphomas is emphasized from various aspects.