Background: Localized and extensive clinical subtypes of alopecia areata (AA) including alopecia totalis and alopecia universalis differ in genetic and immunologic aspects. Objective: Comparison of epidemiologic aspects of localized and extensive subtypes of AA. Patients and Methods: In a prospective descriptive study, 180 patients suffering from AA attending the skin clinics of Razi Hospital in Tehran in 6-month period were studied. The epidemiological aspects of the disease including age at onset, duration, family history, and mental stress were compared in the localized and extensive subtypes of AA. Results: The age at onset was 13.2 years in localized and 19.3 years in extensive AA (P<0.05). The duration of disease was remarkably longer in the extensive form (42.5 months vs. 17.5 months in localized AA). The role of mental stress was mentioned in 55.6% of cases with extensive form and 27.8% of cases with localized AA (P<0.05). There was no relation between family history of AA and the clinical subtype of disease. Conclusion: Extensive AA begins at a younger age, has longer course, and stronger relation with stress.