Dizziness is prevalent in all adult populations, causing considerable morbidity and utilization of health services. In the community, the prevalence of dizziness ranges from 1.8% in young adults to more than 30% in the elderly. In the primary care setting, dizziness increases in frequency as a presenting complaint; as many as 7% of elderly patients present with this symptom. Classification of dizziness by subtype (vertigo, presyncope, disequilibrium, and other) assists in the differential diagnosis. Various disease entities may cause dizziness, and the reported frequency of specific diagnoses varies widely, depending on setting, patient age, and investigator bias. Life-threatening illnesses are rare in patients with dizziness, but many have serious functional impairment. Dizziness can be difficult to diagnose, particularly in elderly persons, in whom it often represents dysfunction in more than one body system. Given the relatively underdeveloped state of the empirical literature on dizziness, investigators would benefit from use of consistent criteria to describe dizziness symptoms and establish diagnoses. Investigation of the effects of testing and treatment should focus on diagnoses that are life threatening or lead to significant morbidity. In the elderly, a function-oriented approach should be studied and compared with current diagnosis-focused strategies. Alternative therapies for chronic and recurrent dizziness also merit investigation.