A quantitative analysis has been made of elastic interactions in three types of pile‐up groups of dislocations in MgO crystals; (i) single pile‐up, (ii) double pile‐up on two orthogonal slip planes, and (iii) double pile‐up on two slip planes intersecting at 120°. The equilibrium positions of dislocations in these groups are given. It is found that the stress concentration factor is highest in type (iii) and lowest in type (i). The number of dislocations in the pile‐up groups sufficient to raise the tip stress to 1000&sgr;0is 1000 in type (i), about 120, determined by extrapolation, in type (ii), and 62 in type (iii).