Recent progress on the study of neutron‐rich unstable nuclei is reviewed. Density distributions of halo nuclei Be and Li are discussed in relation with the medium‐ and high‐energy reaction cross sections with various targets. It is pointed out that the enhancement of the cross sections of halo nuceli is described well by the Hartree‐Fock densities calculated under the constraint for the separation energy. There is no indication of the large deformation in the experimental data of the reaction cross sections, the projectile fragmentations and the Q‐moments of halo nuclei. Multipole resonances in the nucleus10He are studied by using self‐consistent Hartree‐Fock+RPA response function theory. A bunch of resonances with multipolesJ&pgr;=0+,1−and 2+is found near the thresholdEx∼l MeV having significant portions of the sum rule values with narrow widths. The long‐range feature of the Hartree‐Fock potential reflecting the tail of the loosely‐bound neutrons is responsible for the bunching of the resonances.