The problem of interaction among cracks, including the effects of proc
ess zones, is studied. The Dugdale-type cohesive-zone model is extende
d to mixed-modes of loading and is then used to evaluate the size of p
rocess zones. The interaction is considered by applying uniform normal
and shear tractions on each crack surface caused by the remaining cra
cks. The magnitude of these interaction tractions relative to far-fiel
d stresses reflects the intensity of the interaction. The effect of pr
ocess zones on the magnitude of interaction tractions is studied by co
mparing them with the corresponding elastic values. It is shown that p
rocess zones generally enhance the interaction, but effective properti
es are not altered significantly.