BACKGROUND: The posterior interscalene block has been described as an alternative to the lateral interscalene block. However, this technique has not gained popularity because of the close proximity of the approach to vascular and central neural structures.OBJECTIVE: To describe the posterior interscalene block technique using ultrasound imaging, and to review the history of its evolution.METHODS: The use of ultrasound imaging to facilitate the insertion of interscalene catheters using the posterior approach in 11 patients undergoing total shoulder arthroplasty is described.RESULTS: All 11 patients had satisfactory analgesia in the first 24 h of the postoperative period. None of the patients complained of neck pain, as had been found in earlier techniques using the posterior approach.CONCLUSIONS: This modification of the posterior approach is a safe and effective method for the insertion of interscalene brachial plexus catheters. These catheters are also comfortable for patients and, in the present study, none of the catheters inadvertently fell out.