It is difficult to diagnose cerebellar infarction in the territory of the posterior inferior cerebellar artery (PICA) except in cases of Wallenberg's syndrome, because CT and angiography (except with MRI) show no definite abnormalities. There have been few neurootological studies on the relationship between vertigo and cerebellar infarction in the PICA area. We did neurootological studies on 5 patients in the early stage of cerebellar infarction in the PICA area. Their chief complaints were rotatory vertigo with occipital headache. All 5 were over 40 years of age and had risk factors for cerebrovascular disorder : hypertension, diabetes mellitus, hyperlipidemia and or arrhythmia. In 2 of the 5 patients, abnormal neurootological findings had already disappeared when they were examined in the hospital. Therefore, it was particularly important to ask them about their medical history in detail. The other 3, had significant neurootological findings : lateral gaze nystagmus and severe equilibrium disturbance due to truncal ataxia (3 patients); spontaneous horizontal rotatory nystagmus (the rotatory component was dominant) and direction-changing positional nystagmus towards the uppermost ear and positioning downbeat nystagmus (2 patients); spontaneous downbeat nystagmus (1 patient); extension of duration time on caloric testing; reduction of visual suppression on visual suppression test (1 patient). Two patients when MRI showed an abnormal region in the cerebellar vermis had many abnormal neurootological findings. In most cases of cerebellar infarction of the PICA, MRI is necessary for the final confirmation of the diagnosis; however, we consider the medical history and neurootological examinations are also very valuable tools to be used in the clinical diagnosis.