Abstract: The invention relates to a method and a device for prevention of collision between two mutually and independently movable bodies (A, B). In the method the outer contour of each body is approximated by a number of virtual subvolumes, preferably spheres (SA.sub.1, SA.sub.2), whereafter the position of the centrum point (c.sub.1, c.sub.2) of each such sphere, when the respective body assumes a zero or reference position, is stored in a fixed memory together with the radius (r.sub.1, r.sub.2) of each sphere. Repeatedly during a motion the new position of each sphere (SA.sub.1, SA.sub.2) is determined by means of the stored positions and the output signals from position transducers associated to the bodies (A, B) and finally the distance between each sphere of one body (A) and each sphere of the second body (B) is calculated. These calculated distances indicate the risk for collision and must exceed a given threshold value.