Background: Livedoid vasculitis is a distinctive dermatosis characterized by recurrent chronic ulceration and infiltrated purpuric papules on the lower limbs. Objective: The purpose of this study was aimed at evaluating the clinical and histopathological features of livedoid vasculitis. Methods: The hospital charts and histopathologic slides of patients with livedoid vasculitis diagnosed at Asan Medical Center from 1989 to 1999 were reviewed. Results: Twelve male and seven female patients were enrolled in this study (M: F=1.7: 1). The mean age at onset was 30.3 years in men and 25.3 years in women. The mean duration of illness was 3.3 years in male patients and 5.7 years in female patients. All the patients were presented with recurrent chronic ulceration and atrophic scarring. Twelve patients (63.2%) complained of severe pain and tenderness of the lesions and 5 patients (26.3%) complained of itching sensation. In three patients (15.8%), the lesions developed or aggravated in summer. Alcohol intake was aggravating factor in two patients (10.5%) and smoking was in one patient (5.3%). In five patients (26.3%), livedoid vasculitis develops in association with several diseases. Associated diseases were diabetes mellitus in 2 patients (10.5%), antiphospholipids antibody syndrome in 2 patients (10.5%), and protein S deficiency in 1 patient(5.3%). Histopathological examination revealed hyalinized blood vessels, partial to complete obstruction of dermal blood vessels with fibrinoid thrombi, endothelial swelling, and extravasation of RBCs in upper and mid-dermis. Panniculitis-like feature was common finding (73%). In six patients (31%), moderate to severe inflammatory reaction was observed in dermis. Five patients were treated with aspirin, dipyridamole, and pentoxifylline, and among them, only l patient (20%) were improved. All the treatment response including pentoxifylline alone, or pentoxifylline plus aspirin, dipyridamole, or corticosteroid was unsatisfactory. In cases of three patients whom were treated with low-dose danazol, all the patients (l00%) showed marked improvement. One patient was treated with dapsone with improvement. Conclusion: Livedoid vasculitis is a distinct dermatosis with characteristic clinico-pathological features. Low-dose danazol or dapsone may be useful therapeutic options in this intractable disease. (Korean J Dermatol 2001; 39(2): 147~154)