Tumor necrosis factor (TNF) is a prototypical inflammatory cytokine with a wide spectrum of biological activities. Therefore it could play a role in many immunologic and non immunologic disorders. We made a review of the literature concerning the significance of high TNF serum levels in pediatrics and also reported our preliminary results on TNF-alpha values in several pediatric immunologic diseases. Our data seem to confirm the importance of TNF in many immunologic disorders and suggest the opportunity of a more extensive analysis of TNF-alpha serum levels in pediatrics.