We study brane configurations which correspond to N = 1 field theories
in four dimensions. By inverting the order of the NS 5-branes and D6-
branes, a check on dualities in four dimensional theories can be made.
We consider a brane configuration which yields electric/magnetic dual
ity for gauge theories with SO(N-c1) x Sp(N-c2) product gauge group. W
e also discuss the possible extension to any alternating product of SO
and Sp groups. The new features arising from the intersection of the
NS 5-branes on the orientifold play a crucial role in our construction
. (C) 1998 Elsevier Science B.V.