We use type IIB brane configurations which were recently suggested by Hanany
and Zaffaroni to study four dimensional N=1 supersymmetric gauge theories. We
calculate the one loop beta function and realize Seiberg's duality using a
particular configuration. We also comment on the anomaly cancelation condition
in the case of chiral theories and the beta function in the case of chiral and
SO/Sp theories.Comment: 11 pages, Latex. 5 figures. Several changes in text and a reference
was added. Accepted to Phys.Lett.
