hep-th/9801207 Gauge Theories with Tensors from Branes and Orientifolds Authors: Csaba Csaki, Martin Schmaltz, Witold Skiba, John Terning Journal-ref: Phys.Rev. D57 (1998) 7546-7560 We present brane constructions in Type IIA string theory for N=1 supersymmetric SO and Sp gauge theories with tensor representations using an orientifold 6-plane. One limit of these set-ups corresponds to N=2 theories previously constructed by Landsteiner and Lopez, while a different limit yields N=1 SO or Sp theories with a massless tensor and no superpotential. For the Sp-type orientifold projection comparison with the field theory moduli space leads us to postulate two new rules governing the stability of configurations of D-branes intersecting the orientifold. Lifting one of our configurations to M-theory by finding the corresponding curves, we re-derive the N=1 dualities for SO and Sp groups using semi-infinite D4 branes.