Head-up tilt (HUT) has long been used to examine heart rate and blood pressure adaptation to changes in position. During such studies, incidental observations noted that some test subjects experienced total or near-total transient loss of consciousness and that, in some cases, hypotension was associated with unexpected marked bradycardia compatible with a vasovagal syncope (VVS) reaction. The first report of HUT as a clinical tool to confirm a diagnosis of suspected VVS was published in 1966, and led to the concept of using HUT as a diagnostic tool for VVS. Subsequently, HUT testing, either drug-free or, if necessary, with pharmacological provocation (usually nitroglycerin) has proven to be a useful and safe modality for identifying susceptibility to VVS. In this regard, it is recognized that VVS is best diagnosed by careful history taking. Unfortunately, the history may be non-diagnostic; HUT may be helpful in such cases. However, the interpretation of HUT requires care and experience; in particular, the outcome must be consistent with the patient's clinical presentation. The reproduction of patient symptoms may not only provide a diagnosis, but also offer some comfort to the patient and family in that the medical team has documented the basis of symptoms and are thereby positioned to address therapy.