A specific study of the effect of three ingredients in biscuit dough (sugar; fat and water) and of the protein content of the flour has allowed the determination of their respective effects on mixing, on the rheological behaviour on biscuit size after cooking and on their mechanical properties. Addition of sugar to the formula decreases dough viscosity and relaxation time. It promotes biscuits length, and reduces their thickness and weight. Biscuits which are rich in sugar ave characterized by a highly cohesive structure and a crisp texture. Addition of fat softens the dough and decreases the viscosity and relaxation rime. Fat likewise contributes to an increase in length and to a reduction in thickness and weight of biscuits, which are then characterized by a friable structure, easy to break. Increase in water leads to an significant decrease in the dough viscosity and a slight reduction of the relaxation time. The biscuits expand lengthwise, with a smaller thickness. Finally, varying the protein content of the flour from 14 to 20% induces major changes at the mixing stage in the rheological properties of the dough and in the dimensions and texture of the biscuits.