  We present a detailed discussion of the particle spectrum of the Non-Minimal
Supersymmetric Standard Model (NMSSM), containing two Higgs doublets and a
singlet, in the limit $\tan\beta \simeq m_t/m_b$. This is compared with the
corresponding particle spectrum of the Minimal Supersymmetric Standard Model
(MSSM). In this limit the singlet vacuum expectation value is forced to be
large, of the order of $10$ TeV, and the singlet decouples from the lightest
scalar Higgs boson and the neutralinos. With the exception of the lightest
Higgs boson, the particle spectrum in the model turns out to be heavy. The
radiatively corrected lightest Higgs boson mass is in the neighbourhood of
$\sim 130$ GeV.
