Abstract: The paper indicates the regularity of stress distribution over the sections of log grips by means of photoelastical method. It is concluded that the grips of vertical elliptical, circular and horizontal elliptical contour are stressed favourably. Under unfavourable work conditions a dangerous section forms on the inner wing of the joint between sprag and grip, where the stresses are concentrated. It is possible to determine the allowable gripping strenth of the grips made of various materials and of various section sizes, and furthermore, to design the gripping device with horizontal elliptical grips, using the data and formulae derived from the experiment.