Defective butt joints in sandwich structures create the presence of 90° corners from which fracture is very likely to be initiated due to the stress intensification caused by the geometric and material discontinuity at the corner. In this article the singular stress field, both the singularity and the stress intensity factors, at the bimaterial comer are computed, and the field amplitudes obtained are then used to predict the onset of damage growth in sandwich beams with bimaterUti corners of different material combinations. A parametric study is used to develop an empirical relation between stress intensity factors and geometric and material parameters. Static strength predictions are compared with tests of sandwich beams with simulated defective butt joints, and the correlation is satisfactory. It is concluded that great care must taken in manufacturing to avoid flawed butt joints, which have a large influence on the load-bearing capacity.