Interscalene block was first described in 1970 by Alon Winnie. The interscalene approach to the brachial plexus makes it possible to reliably anesthetize the shoulder as well as the remainder of the upper extremity. Whereas the first description of the interscalene brachial plexus block was by paresthesia technique, the block is equally well suited to nerve stimulator technique. Both techniques are covered in detail below, including helpful clinical tips to increase success rates while minimizing complications. Side effects and complications of interscalene block include phrenic nerve paresis, neuropraxia, Horner's syndrome, hoarseness, cough, and bronchospasm. These side effects and complications are based upon the anatomy of the brachial plexus at this level. Physiological implications and management of these side effects/complications are presented. Careful attention to technique, anatomy, and insistence on an alert or minimally sedated patient are critical to successful practice.