This study was undertaken to investigate the skin sensitivity to 54 different allergens in 248 patients of 81 acute urticaria, 141 chronic urticaria and 26 atopic dermatitis, who visited in Department of Dermatology, College of Medicine, Chung Ang University Hospital from February 1986 to January 1987. The results were as follows . 1. The sex ratio of male to female of 248 patients with allergic state was 1.1: 1 (130: 118) and third and fourth decades occupied 56.5%. In regard to the duration of chronic urticaria, less than 1 year were 31.2% and between 1 to 3 years were 28.3%. 2. In acute urticaria, the prick test positive reactivity to allergens were in descending order to mite, household insect mixture, Trichophyton mixture, house dust, mold mixture C and silk, whereas in chronic urticaria ', mite, household insect mixture, house dust, cockroaeh mixture, Trichophyton mixture and silk and in atopic dermatitis ; mite, house dust, Trichophyton mixture, household insect mixture, mold mixture A and C. 3. The positive reactivities of allergens in patients with atopic dermatitis, chronic urticaria and acute urticaria were 69.2%, 52.5% and 35.8%, respectively. 4. The positive reactivity to compound allergens were higher than to single and the most frequent combinations were 2 to 5 allergens (85.4%). 5. Out of 54 allergens used in this study, 49 allergens were reactive and the most frequent group of allergens were house dusts (41.5%) and commonly involved allergens were mite (27.8%), household insect mixture (15.7%), house dust (13.7%), Trichophyton mixture (11.7%) and cockroach mixture(7.7%). 6. Common other allergic diseases combined with atopic dermatitis were rhinitis and bronchial asthma, occuring in 23.1%.