  We discuss tree level three and four point scattering amplitudes in type II
string models with matter fields localized at the intersections of D-brane
wrapping cycles. Using conformal field theory techniques we calculate the four
fermion amplitudes. These give "contact" interactions that can lead to flavour
changing effects. We show how in the field theory limit the amplitudes can be
interpreted as the exchange of Kaluza-Klein excitations, string oscillator
states and stretched heavy string modes.
