A test specimen was developed that gave a constant value of the stress intensity factor in Mode I under prescribed displacement loading conditions. The test specimen was a double contoured cantilever beam specimen, derived from beam theory. The stiffnesses needed in the analysis and the stiffness as function of crack length were determined by use of the finite element method. For the final shape the valid range of crack extension was established. It is believed that the specimen could be useful for many applications where a constant stress intensity factor is needed, such as viscoelastic crack growth in an adhesive layer.