Abstract: This research concerns the study of mechanical behaviour of this material at high temperature. It is a question of observing dislocations microstructure in monocrystaline rutile by Tranmission Electronic Microscope (T.E.M.). This investigation method requires very thin foils, cut out in deformed sample. Thus it is necessary to develop a method to obtain an important dislocation density in restricted zone of the sample. The solution is to obtain three points bent sub-boundaries. For this purpose the chosen solution consists to stir only one slip system and then proceed to a polygonization.The slip system to stir is of the type {101}<î 01>. From a rutile monocrystal, samples have been cut, suitably oriented using X rays by laue method. After mechanical polishing, samples have ben strained in three points bent at 1000�C then annealed at 1300�C during 12 h. The sub-boundaries were observed by optical microscope by eth-pits which consists to chemical polishing by alkaline fusion in KOH followed by an immersion in boiling sulphuric acid during 2 to3 min. It is sub-boundaries of very weak disorientation. Practically all concentrates in central zone of the sample. The rutile being a ceramic chemically weak stired, thin foils have been obtained by ionic bombardment thinning method. The T.E.M. observation have allowed to characterize the dislocations forming the sub-boundaries corresponding to dislocations arrangement of corner type, located in the same plan.