  We consider the supersymmetric extension of the standard model with an
additional singlet $S$, the Non-Minimal Supersymmetric Standard Model (NMSSM),
in the limit $\tan\beta \simeq m_t/m_b$. We embed this model in a supergravity
framework with universal boundary conditions and analyze the renormalization
group improved tree-level potential. We examine the relationship between this
model and the minimial supersymmetric standard model (MSSM), and discuss the
novel connections between the two when $\tan\beta$ is large. Strong
correlations between the free parameters of the nonminimal model are found and
the reasons for these discussed. The singlet vacuum expectation value is forced
to be large, of the order of $10 TeV$. The radiatively corrected mass of the
lightest Higgs boson is found to be $\stackrel{_<}{_\sim} 140 GeV$.
