Every tumor cell is equipped with an array of biologically active surface molecules, and several of these function as receptors for various ligands. They include MHC, or in the case of humans, HLA antigens, cytokine receptors, cell-adhesion molecules, growth factor receptors, Fas/Fas-ligand molecules and others. Their expressions are a subject to alterations, usually to the advantage of tumor growth and spread. Some appear on tumor cells de novo, having no counterparts on the respective normal cells. Detailed knowledge about the expression of tumor-cell receptors and their genotypes, in particular of cancerous ones, may provide information essential for the creation of tools for specific tumor immunotherapy.