The depth-survival effect of a beta-delayed particle decay ~9C beam on human salivary gland (HSG) cells is presented in this paper. Compared with a stable ~(12)C-ion beam, the radioactive ~9C-ion beam showed an enhanced biological effect, i.e., remarkably enhanced efficiency in cell killing, at the penetration depths around its Bragg peak. The biophysical mechanisms underlying the enhanced biological effect are discussed herein, and the latest progress in biological effect induced by another radioactive 8B-ion beam is introduced. In the end of this paper, several topics concerning the frontier of the radiation-induced biological effects using radioactive ion beams are proposed.