The effective interaction method, traditionally used in the framework of a
harmonic oscillator basis, is applied to the hyperspherical formalism of fe
w-body nuclei (A = 3 - 6). The separation of the hyperradial part leads to
a state dependent effective potential. Undesirable features of the harmonic
oscillator approach associated with the introduction of a spurious confini
ng potential are avoided. It is shown that with the present method one obta
ins an enormous improvement of the convergence of the hyperspherical harmon
ics series in calculating ground state properties, excitation energies, and
transitions to continuum states.