Kikuchi's disease (necrotising lymphadenitis) is characterised by cervical lymphadenopathy in young patients and may be mistaken for malignant disease both clinically and histologically. Microscopically, there is a varying degree of effacement of the lymph node architecture and necrosis with an infiltrate of "histiocytic" cells and absence of polymorphs. The disease is of unknown aetiology. It was originally described in Japan, and only 27 cases have been reported elsewhere (none in the United Kingdom), although it has probably been seen but not recognised. The clinical, histopathological, electron microscopic, and immunohistological findings in four cases of the disease were evaluated.