Abstract This article reviews and summarizes randomized, controlled studies that have assessed ultrasound (US) guidance for brachial plexus blocks in comparison with other nerve localization methods as well as those that have compared different US-guided brachial plexus block techniques. Both PubMed and EMBASE databases were searched using the MeSH terms anesthetic technique, brachial plexus, and ultrasound. Studies were included if they had randomized allocation comparing US with another conventional nerve localization technique or if they compared 2 different US-guided techniques, such as single versus multiple injections. Each study was classified as a categorical outcome as being supportive, unclear, or negative for the use of US. These were compared with χ² analysis with the null hypothesis that US provides no benefit for brachial plexus blocks. Forty-seven studies met the inclusion criteria, and 29 compared US guidance to landmark or peripheral nerve stimulation techniques. Our analysis of the literature supports the use of US over other nerve localization techniques as being beneficial for several block performance outcomes including block performance time, reducing the number of needle passes and the incidence of vascular puncture, shortening sensory block onset time, and improving block success.