The mechanical properties of short-dough biscuits of various composition were determined in three-point bending tests. In general, reduction of fat content increased the modulus and the fracture stress of biscuits. The relative magnitude of this effect depended on the fat type. Sucrose syrup slightly enhanced the brittle character of biscuits, compared with crystalline sucrose, indicating that sucrose crystals were not the fracture-inducing defects. Substituting starch for part of the flour had relatively little effect on the mechanical properties. Sugar-free biscuits had a significantly lower modulus and fracture stress. Differential scanning calorimetry showed that, irrespective of composition, starch gelatinisation was slight, presumably due to the limited water content coupled with the low baking temperature. It is concluded that biscuits comprise a glassy matrix; their mechanical properties are mainly determined by air and fat volume fraction as well as the size of inhomogeneities. © 1999 Academic Press.