The objective of the project was the determination of conditions producing stick-slip effect during shear test of food powders and the examination of the influence of speed and stiffness of apparatus on their flowability. Experiments were performed in a shear tester of 60 mm in diameter for four different food powders: corn flour, wheat starch, potato starch and fine potato starch. For all of the materials examined, oscillations of shear stress vs. displacement experimental curves were observed, for all speeds and stiffness values, except for potato starch at 2 mm min-1 and lower stiffness. Changing the speed of deformation in the case of wheat flour, fine potato starch and potato starch did not cause changes in the values of flow functions. In the case of corn flour, an increase in speed resulted in flow functions of values characteristic for cohesive materials.