Since the first report on the use of mutants lacking enzymes and HAT medium for hybrid selection (Littlefield, 1964), enormous similar techniques, at least, have been basically established. These techniques have opened new avenues to assigning genes, analysing gene regulation in eukaryotic cells and studying mechanisms which govern cell growth and differentiation during normal embryonic development, wound healing and tumor formation. But some problems still remain. For instance, such techniques need about one year to mutate both kinds of cells before fusion and selection, A simple technique of somatic cell hybridization without cell mutation has been developed, and by utilizing different appearances of cells before and after trypsinization, two kinds of cells may be fused and selected in some hours. Up-to-date six kinds of cells have been tested and found successful. Some hundreds of tests have been repeated, and modified, and the analyses by different methods have shown that the technique is both stable and reliable.