AbstractA method is proposed for the study of growth, under normal internal pressure, of pre‐existing hydraulically induced planar cracks. The continuous growth process is approximated by a stepwise one, and during each growth step the volume of fluid within the crack cavity is assumed constant. The normal distance through which each point on the crack edge moves outwards is controlled by the level of stress intensity factorKIat each point, and the crack‐resistance characteristics of the material, which can be expressed by some critical level ofKI, denoted byKIC. For the present study, that distance was assumed proportional to (KI−KIC)4forKI>KIC. The evaluation ofKIat the crack edge is achieved by utilizing the method discussed by Mastrojanniset al.1The proposed method was applied to the study of the initial stage of growth of a circular crack under linearly varying normal pressure, and of an elliptical crack under uniform normal pre