This invention discloses two new VEGI isoforms named VEGI-.sub.192a and VEGI-.sub.192b consisting of 192 amino acid residues. These isoforms show endothelial cell-specific expression and share a C-terminal 151-residues segment with the previously described VEGI-.sub.174 and VEGI-.sub.251. Methods of using these isoforms of VEGI in diagnosing, screening agonist and antagonist of the isoforms, and treating various angiogenesis-related diseases are also disclosed.