DNA sequences coding for a TNF-binding protein and for the TNF receptor of which this protein constitutes the soluble domain. The DNA sequence can be used for preparing recombinant DNA molecules in order to produce TNF-binding protein and TNF receptor. Recombinant TNF-binding protein is used in pharmaceutical preparations for treating indications in which TNF has a harmful effect. With the aid of the TNF receptor or fragments thereof or with the aid of suitable host organisms transformed with recombinant DNA molecules containing the DNA which codes for the TNF receptor or fragments or modifications thereof, it is possible to investigate substances for their interaction with the TNF receptor and/or for their effect on the biological activity of TNF.