In this talk I will consider brane configurations that include NS5 branes, orientifold planes and anti-branes. I will argue that the class of field theories that live on such brane configurations admit Seiberg duality. Interactions between branes and orientifold planes will be given a field theory interpretation. In particular a certain repulsive interaction will lead to a non-trivial Coleman-Weinberg potential and dynamical symmetry breaking. I will also discuss the case of type 0' strings and chiral symmetry breaking of the form SU(Nf)xSU(Nf)-->SU(Nf) in a QCD-like theory.