Posterior bone block is one of the surgical procedures proposed in the literature for posterior instability of the shoulder. Prognosis is better in traumatic than in atraumatic instability. Voluntary subluxations with true intentional episodes are a contraindication for surgery. To have an accurate and reproducible technique, we recommend 7 surgical steps: (1) Vertical deltoid approach, (2) Horizontal infraspinatus splitting approach, (3) Medial T-shaped arthrotomy, (4) Joint exploration and treatment of labral lesions, (5) Abrasion of posterior glenoid cortex, (6) Harvesting and preparation of an accurately sized and shaped iliac graft, and (7) Cautious fixation of the graft with 2 low compression screws. Association with capsulorrhaphy and/or glenoid osteotomy may be necessary, respectively, in cases of hyperlaxity and/or excessive glenoid retroversion. The best treatment of patients who have recurrent posterior instability of the shoulder remains controversial. Precise, specific, and durable rehabilitation prior to surgical treatment has been universally recommended.1-7 If this program fails to relieve the patient's symptoms, a great variety of surgical procedures have been proposed: soft-tissue procedures (posterior capsulorrhaphy, reverse Putti-Platt, biceps tendon transfer), osteotomy of the glenoid, rotational osteotomy of the humerus, and posterior bone block. Various combinations of these procedures have also been proposed. Posterior bone block is not the most popular procedure that has been recommended in this pathology but it is our preferred method, alone or in combination with posterior capsulorrhaphy and/or glenoid osteotomy.