Patients who showed an inhibitory pattern at the first assessment had a continuous improvement in V-HIT performance, while patients with an initial excitatory response had a transient decrease in gain at the subsequent evaluation (P=.001). Hyperventilation, hyperventilation induced nystagmus, nystagmus, vertigo, vestibular neuritis, vestibulo-ocular reflex INTRODUCTION Hyperventilation-induced nystagmus test (HINT) is a procedure that can be easily performed during a bedside evaluation of dizzy patients without causing them excessive stress.1 It is well reported that the metabolic changes induced by hyperventilation can elicit a nystagmus in various vestibular disorders and that HINT can be used to reveal vestibular imbalance due to its ability to bring out asymmetries both at a central and a peripheral level.1-2-3 A unique feature of the HINT is its capability to generate a nystagmus in the absence of any dynamic stimulation of the labyrinth and, for this reason it has good sensitivity in cases of diseases that involve the central nervous system or the vestibular nerve.2-4-5-6 A positive test has been reported in 91.7% of cases of acoustic neuroma, in 75% of cases of multiple sclerosis, and in 72.7% of cerebellar diseases.5 Acute unilateral vestibular neuritis, also called acute unilateral vestibulopathy (AUVP), is one of the most common causes of vertigo. The excitatory response is less common; it can be observed almost exclusively during the acute phase, and it tends to be replaced by an inhibitory pattern during the follow-up.8The test seems to correlate with the severity of dizziness, but a clear prognostic value has not yet emerged.9 Aim of this study is to indicate the clinical role of HINT in AUVP, in particular the correlation between the evoked pattern and the gain of the vestibulo-ocular reflex (VOR) evaluated with the video head impulse test (V-HIT). All the patients fulfilled the criteria for acute unilateral vestibulopathy according to the Barany Society: presence of spontaneous unidirectional nystagmus, history of rotatory vertigo with an acute onset lasting more than 24 hours, positive clinical head impulse test (HIT), absence of hearing loss, and contralateral normal vestibular and cochlear function.7 In order to have a homogeneous group, we selected patients who showed signs of superior vestibular neuritis.