Unilateral keratosis fotlicularis has the same histological features of classic Dariers diseases and is considered to be a localized variant of Dariers disease. Unlike classic Dariers disease, it is not related to family history but with a later age of onset, unilateral and linear lesions. Lar,k of solar aggravation and increase,d irritation from sweating also characterize this disease. A 45-year-old female presented with scaly follicular papules in a linear distribution limited to one side of her lower extremity. There was no family history or other signs of Dariers disease elsewhere in the body. Histopathological features were typical of acantholytic dyskeratosis. The condition was aggravate~d during the summer and regressed with residual pigmentation after topical application of corticosteroid and tretinoin. (Kor J Dermatol 1996;34~(6): 1008 1012)