C. Atkinson: Concerning calculations of the interaction of arrays of dislocations, or slip bands and cracks such as those considered by prof. Yokobori, I would like to point out a possible simplification. A closed form solution to the problem of the interaction of a dislocation and a crack.in any orientation in plane strain or stress in a general anisotropic medium was given by Atkinson (Int. J. Fract. Mech., Dec. 1966), and this can be used for dislocation array problems by simple superposition. If the dislocations are considered as smoothed out or in equilibrium, the corresponding integral equation or set of simultaneous equations can be written down. Thus we only have to solve the problem for the integral over the slip band, or array of dislocations, the problem of annulling the stress over the crack being already solved. Reply by T. Yokobori: Unfortunately the J. Frac. Mech., Dec. 1966, had not yet been distributed when we worked out this problem. At any rate, your calculations concern the interaction of a 'single' dislocation and a crack, but ours concern the interaction of distributed dislocations (slip band) and a crack. That is the important difference.