We determine the vacuum structure and phases of N = 1 theories obtained via
a mass mu for the adjoint chiral superfield in N = 2, SO(n(c)) SQCD. For l
arge number of flavors these theories have two groups of vacua. The first e
xhibits dynamical breaking of flavor symmetry USp(2n f) --> U(n f) and aris
es as a relevant deformation of a non-trivial superconformal theory. These
are in the confined phase. The second group, in an IR-free phase with unbro
ken flavor symmetry, is produced from a Coulomb branch singularity with Sei
berg's dual gauge symmetry. In the large-mu regime both groups of vacua are
well-described by dual quarks and mesons, and dynamical symmetry breaking
in the first group occurs via meson condensation. We follow the description
of these vacua from weak to strong coupling and demonstrate a nontrivial a
greement between the phases and the number of vacua in the two regimes. We
construct the semiclassical monopole flavor multiplets and argue that their
multiplicity is consistent with the number of N = 1 vacua. (C) 2001 Publis
hed by Elsevier Science B.V.