The isomorphic response of Koebner is a well-known phenomenon commonly associated with psoriafsis, but it has been also descrilbed in conjunction with a host of other disordered. We described five cases of erythema multiforme showing lesions of easily recognizsble Koebnei phenomena. Traumas to the skin do not cause erythema multiforme, however when a patient is in an active stage of the disease, physieal factor such as traumas occuring in normsl daly-life may contribute to the distribution of skin lesions as have been seen in our patients ; clinicians should aware of this point for better understanding of clinical features in erythema multiforme. (Kor J Dermatol 1993;31(4):581-585)