According to various studies, Grain Boundary Engineering (GBE) is likely to enhance mechanical properties of polycrystalline materials. The present investigation highlights some relationships between thermomechanical process (TMP) parameters of a commercial nickel-base superalloy PER72, supplied by Aubert & Duval (equivalent to Udimet®20™) and the resulting microstructure. The long-term goal is to develop TMPs that modify the Grain Boundary Character Distributions (GBCD) in order to improve high temperature properties. In this context, Grain Boundary Engineering (GBE) techniques are considered, thinking of replacing standard forming processes by optimised thermomechanical treatments. Mechanical testing at high temperature (compression and torsion tests) has been carried out and it is shown that multi-step treatments promote twinning. Some clues are then presented in an attempt to explain when and how twins are created. © (2010) Trans Tech Publications.