Background: Triangular alopecia, previously known as temporal or congenital triangular alopecia, is a kind ofalopecia typically observed in infants and children. Triangular alopecia is rarely reported, and little is known aboutits histopathology and response to treatment.Objective: To describe the clinical and histopathological features, as well as response to treatment of triangularalopecia in Korean patients.Methods: A total of 15 patients, diagnosed at our department from 2000 through 2012, were evaluated.Results: All patients were presented with a triangular or oval, skin colored hairless patches on the frontotemporalsutureline, except one patient who had hairless patch on the occipital sutureline. Average age of onset was 4.13years old and there was no sexual predilection. The histopathologic features were similar in all patients with a fewvellus hairs, no terminal hair and without any abnormalities at the epidermis and dermis. Ten out of 15 patientswere treated with topical minoxidil solution and 2 patients showed mild improvement.Conclusion: Some cases of triangular alopecia are recognized at birth; however, other cases appear to developduring the first three or four years of life. These later development can be best explained as a result of hairminiaturization leading to vellus hair formation. (Korean J Dermatol 2012;50(12):1042∼1046)