This invention relates to a general methodology for efficient creation of trimeric soluble receptors for therapeutic applications. The process involves gene fusion between a soluble receptor with a ligand binding domain and a trimerization tag from the C-propeptide domain of pro-collagen, which is capable of self-assembly into a covalently linked trimer. Using both in vitro bioassays and an in vivo mouse model for collagen-induced arthritis (CIA), we show that the homotrimeric soluble TNF receptor produced with such method is a more potent blocker than dimeric TNF receptor decoys in inhibiting TNF-.alpha. mediated inflammatory diseases.