  We address the two main questions relevant to microscopic nuclear structure
calculations starting from a free NN potential. These concern the accuracy of
these kinds of calculations and the extent to which they depend on the
potential used as input. Regarding the first question, we present some results
obtained for nuclei around doubly magic 132Sn and 208Pb by making use of an
effective interaction derived from the Bonn A potential. Comparison shows that
our results are in very good agreement with the experimental data. As for the
second question, we present the results obtained for the nucleus 134Te by
making use of four different NN potentials. They indicate that nuclear
structure calculations may help in understanding the off-shell nature of the NN
potential.
