We conducted a clinicopathologic study of 79 cases of Kikuchi's disease. Our results confirmed that Kikuchi's disease is a distinctive type of necrotizing lymphadenitis that affects primarily the cervical lymph nodes of young adults and has a self-limited clinical course. However, female predominance was not as striking as heretofore reported. A low, but possible, recurrence rate of 3.3% was documented. Extranodal cutaneous involvement occurred in one patient who had a more severe and protracted clinical course. Classification of the histopathologic changes into three histologic types was proposed: proliferative, necrotizing, and xanthomatous types. These three types differed in certain aspects of their clinical features. Immunohistologic analysis revealed that the predominant cells of the lesions were various types of histiocytes, including the enigmatic plasmacytoid monocytes. A variable number of CD8(+) T cells correlating with the duration of the disease was detected. B cells were nearly absent, and only an insignificant number of OPD4(+) T cells was present. Eight cases studied by the flow cytometric DNA analysis all showed a diploid DNA content. Although the histologic changes of Kikuchi's disease were variable, the findings were sufficiently distinctive to permit accurate diagnosis. Malignant lymphoma and especially lupus lymphadenitis can be mistaken for Kikuchi's disease; thus differentiation is crucial.