The objective of this paper is to predict the entire stress/ strain curves and the loss of stiffness with damage for sheet-moulding-compound (SMC) composites. This is achieved by developing a statistical micro-macro relationship with the help of the model of Mori and Tanaka. In the case of an SMC composite with a 32% fiber volume fraction, debonding at the fiber/matrix interfaces is the predominant ‘microdamage’ mechanism. In order to relate the microstructure, and its local perturbations, to the macroscopic damaged behaviour, we introduce a statistical local damage criterion and the concept of the equivalent damaged inclusion in the micro-macro relationship of Mori and Tanaka. This paper shows the relationship between the statistical interface failure criterion and the scattering observed on the macroscopic mechanical test results.