This chapter provides a comprehensive overview of electronystagmography (ENG) and videonystagmography (VNG), which are vital diagnostic tools for assessing vestibular function. The physiological basis and the reflex pathways involved in balance and gaze stabilization are described. This chapter outlines the ENG/VNG test battery, including both vestibular (e.g., caloric testing, Dix–Hallpike maneuver) and non-vestibular (e.g., saccade, tracking, and optokinetic) components. Advantages and limitations of these tests are discussed, emphasizing their value in diagnosing peripheral and central vestibular disorders. The role of ENG/VNG in clinical decision-making is underscored, especially when interpreted alongside a thorough neurotologic history and examination.