  Non-perturbative D-brane instantons can generate perturbatively absent though
phenomenologically relevant couplings for Type II orientifold compactifications
with D-branes. We discuss the generation of the perturbatively vanishing SU(5)
GUT Yukawa coupling of type 10 10 5_H. Moreover, for a simple globally
consistent intersecting D6-brane model, we discuss the generation of mass terms
for matter fields. This can serve as a mechanism for decoupling exotic matter.
