  We provide a systematic construction of three-family N=1 supersymmetric
Pati-Salam models from Type IIA orientifolds on $\IT^6/(\IZ_2\times \IZ_2)$
with intersecting D6-branes. All the gauge symmetry factors $SU(4)_C\times
SU(2)_L \times SU(2)_R$ arise from the stacks of D6-branes with U(n) gauge
symmetries, while the ``hidden sector'' is specified by $USp(n)$ branes,
parallel with the orientifold planes or their ${\bf Z_2}$ images. The
Pati-Salam gauge symmetry can be broken down to the $SU(3)_C\times
SU(2)_L\times U(1)_{B-L} \times U(1)_{I_{3R}}$ via D6-brane splittings, and
further down to the Standard Model via D- and F-flatness preserving Higgs
mechanism from massless open string states in a N=2 subsector. The models also
possess at least two confining hidden gauge sectors, where gaugino condensation
can in turn trigger supersymmetry breaking and (some) moduli stabilization. The
systematic search yields 11 inequivalent models: 8 models with less than 9
Standard model Higgs doublet-pairs and 1 model with only 2 Standard Model Higgs
doublet-pairs, 2 models possess at the string scale the gauge coupling
unification of $SU(2)_L$ and $SU(2)_R$, and all the models possess additional
exotic matters. We also make preliminary comments on phenomenological
implications of these models.
