  We discuss the difficulties in testing the hadron models by using the N^*
parameters extracted from the empirical amplitude analyses of the pi-N and
gamma-N reaction data. As an alternative or perhaps a more advantageous
approach, we present a Hamiltonian formulation that can relate the pion
production dynamics and the constituent quark models of N^* structure. The
application of the approach in investigating the Delta and N^*(S_{11})
excitations is reviewed. It is found that while the Delta excitation can be
described satisfactory, the pi-N scattering in S_{11} channel can not be
described by the constituent quark models based on either the
one-gluon-exchange or one-meson-exchange mechanisms. A phenomenological
quark-quark potential has been constructed to reproduce the S_{11} amplitude.
