Despite being the foremost examination in the management of traumatic nerve damage electromyography (EMG) has an uncertain and ill-defined role in the investigation of brachial plexus palsy of the newborn (BPPN). This may be because EMG, which is used most commonly several months after birth, fails to answer adequately two of the most important questions posed by this condition: its aetiology and the likely prognosis. In this review, we contend that EMG has important contributions to the solution of both of these questions but only if the timing of the investigation is altered. Used early on in the first few days after birth, EMG can separate the rare palsies that occurred during the intrauterine period from those caused by events at the time of birth, and thus have an important role in directing the investigations of the aetiology more appropriately. EMG alone would still not be able to determine which of the perinatal events were responsible. If the EMG is then repeated before reinnervation complicates interpretation, it seems probable that it would identify accurately those cases, where neurotmesis and avulsion have occurred, much earlier than 3 months of age, the crucial age in the clinical assessment of BPPN for consideration for surgery. This might have very important implications for the future directions of treatment.