TNF-receptor-associated periodic syndrome (TRAPS) is a recently recognized disorder characterized by prolonged attacks of high fever and severe localized inflammation. TRAPS is caused by dominant mutations in the 55 kDa TNF receptor gene (TNFRSF1A). We here describe three German TRAPS patients of two families with Cys30-->Arg and Thr50-->Met mutations, respectively. Both mutations have already been observed before in other nonrelated families. The Thr50-->Met amino acid exchange, caused by an ACG-->ATG transition, has been reported in two other families of different ethnic background. The possibility that the ACG-->ATG sequence alteration is a mutational hot spot causing TRAPS is discussed. Furthermore, we describe and discuss the symptoms of our patients, possible inducers of febrile attacks, and treatments which the patients had received when their diagnoses were still unknown.