We investigated serum levels of interferon alpha, interferon gamma, tumour necrosis factor alpha, interleukin-2 (IL-2) and interleukin-6 (IL-6) in patients with necrotizing lymphadenitis (Kikuchi's disease) (NL). Four male patients, diagnosed as having NL following biopsy of the affected lymph nodes and by the clinical course, were included in this study. All four patients had higher than normal serum interferon gamma and IL-6 levels during the acute phase, which returned to normal levels during the convalescent phase. Interferon alpha, tumour necrosis factor alpha and IL-2 were, however, within the normal ranges. Our findings indicate the possibility that interferon gamma and IL-6 may play an important role in the pathogenesis of NL.