The extensor indicis proprius muscle (EIPM) is considered a key muscle in the assessment of the level of the neurologic lesion causing any motor or sensory medio-cubital impairment of the hand. The aim of this study is to illustrate the anatomical peculiarities of the EIPM, the ultrasound (US) anatomy of the inferoposterior part of the forearm, and the technique of US-guided electromyography (EMG) of the EIPM. The US-guided EMG of the EIPM is technically easy and safe for young practitioners, provided there is a good knowledge of US anatomy of the inferoposterior part of the forearm.