  We study a bound state of fractional D3/D7-branes in the ten-dimensional
space R^{1,5}*R^{4}/Z_2 using the boundary state formalism. We construct the
boundary actions for this system and show that higher order terms in the
twisted fields are needed in order to satisfy the zero-force condition. We then
find the classical background associated to the bound state and show that the
gauge theory living on a probe fractional D3-brane correctly reproduces the
perturbative behavior of a four-dimensional N=2 supersymmetric gauge theory
with fundamental matter.
