The present application is directed to stabilized HIV envelope glycoprotein trimers. The trimers are stabilized by introducing trimeric motifs, preferably the GCN4 coiled coil or the fibritin trimeric domain, at certain sites, for example in the gp41 ectodomain. These stabilized trimers or DNA molecules encoding such trimers can be used to generate an immunogenic reaction. The trimers can also be used in assays to screen for molecules that interact with them--and to identify molecules that interact with specific sites.