Approximate description of high-lying collective excitations of nuclei

We discuss the one-transition approximation in the RPA equations for description of high-lying isoscalar and isovector collective modes in a double nuclear system of arbitrary configuration. Isospin-mixing effects in asymmetric systems (Nnot =Z) are considered. In application to ordinary nuclei we discuss the structure and spectrum of isoscalar and isovector modes generated by factorized and local residual interactions. In the latter case a justification of the hydrodynamical liquid-drop model is given