Needle electromyography (EMG) records electrical signals generated from muscle fibers and interprets the signals to characterize underlying pathologic changes that are occurring in motor units within muscles. Different types of spontaneously firing waveforms and motor unit potential changes occur with different neuromuscular disorders. The performance of reliable EMG studies depends on the technical skills of the physician in inserting, moving, recording with a needle electrode, and analyzing electric signals recorded from muscle. This article reviews the technique of needle EMG and recognition and interpretation of various EMG waveforms. The author presents several demonstrative videos at www.neurologic.theclinics.com.