This paper presents the results of a combined experimental and theoretical study of the ductile layer toughening of brittle intermetallics. Following a brief description of small- and large-scale bridging models for the estimation of the crack-tip shielding due to small- and large-scale bridging, the effects of ductile layer toughening are examined in a gamma-based titanium aluminide alloy (Ti-48Al) reinforced with TiNb strips; MoSi2 reinforced with Nb layers, and NiAl reinforced with V layers with different thicknesses. In all cases, the measured resistance-curves are well predicted by existing small- and large-scale bridging models. The intrinsic specimen-independent toughness values are also shown to increase with increasing layer thickness, in the case of the NiAl/V composites. Finally, the general implications of the results are discussed for the toughening of brittle matrix composites under monotonic and cyclic loading.