[en] Transfer reactions induced by beams of light nuclei at incident energies of around 10 MeV/nucleon are discussed. For beams of ¹²C this means about 120 MeV in the laboratory system. The potential usefulness of the one-, two-, three-, and four-nucleon transfer reactions as a spectroscopic tool resides in their extreme selectivity. In each spectrum only a few states of the residual nucleus appear, over a wide range of excitation energies; furthermore, the states that are seen usually show up very strongly. The full explanation of these phenomena demands consideration both of reaction theory and nuclear-structure ideas. It appears that heavy-ion transfer reactions have great potentialities for investigating collective clustering effects in nuclei. (Auth.)