The patient was a 48-year-old man who had a history of colonic polyps. About 18 months before, a dark reddish nodule had appeared on his right forearm. By peripheral growth, this lesion had formed a crateriform prominence with central healing. Similar symptoms multiplied and expanded, the largest being about the size of a child's head. Given both the clinical and histologic evidence, a diagnosis of keratoacanthoma centrifugum marginatum (KCM) was made. Oral etretinate was administered, and an involution of verrucous plaque began after 4 weeks. After 8 weeks, the lesions faded, leaving pigmentation in some areas. This is a rare disorder, only 30 such cases having been reported worldwide, and the present case was the third in which oral etretinate was found to be effective. (J Am Acad Dermatol 2003;48:282-5.)