The autoinflammatory syndromes are systemic disorders characterized by apparently unprovoked inflammation in the absence of high-titer autoantibodies or antigen-specific T lymphocytes. One such illness, TNF-receptor-associated periodic syndrome (TRAPS), presents with prolonged attacks of fever and severe localized inflammation. TRAPS is caused by dominantly inherited mutations in TNFRSF1A (formerly termed TNFR1), the gene encoding the 55 kDa TNF receptor. All known mutations affect the first two cysteine-rich extracellular subdomains of the receptor, and several mutations are substitutions directly disrupting conserved disulfide bonds. One likely mechanism of inflammation in TRAPS is the impaired cleavage of TNFRSF1A ectodomain upon cellular activation, with diminished shedding of the potentially antagonistic soluble receptor. Preliminary experience with recombinant p75 TNFR-Fc fusion protein in the treatment of TRAPS has been favorable.