Abstract: The present invention provides a method for identifying a binding molecule having selective affinity for a ligand. The method consists of selectively immobilizing a diverse population of binding molecules to a solid support, simultaneously contacting the diverse population immobilized on the solid support with two or more ligands and determining at least one binding molecule which selectively binds to one or more of the ligands. The invention additionally provides a method for identifying an antibody having selective affinity for a tumor antigen. The method consists of selectively immobilizing a diverse population of antibodies to a solid support, simultaneously contacting the diverse population immobilized on the solid support with two or more tumor antigens and determining at least one antibody which selectively binds to one or more of the tumor antigens. The invention also provides an isolated binding polypeptide selective for a tumor antigen.