Treatment of aggressive keratoacanthomas by radiotherapy. Keratoacanthomas infrequently are treated by radiotherapy. However, keratoacanthomas that are recurrent after surgical excision or whose resection would result in cosmetic deformity may benefit from radiotherapy. Between January 1970 and June 1988, 29 such keratoacanthomas in 18 patients were irradiated. Doses ranged from 3500 cGy in 15 fractions to 5600 cGy in 28 fractions. Measured end points of therapy were (1) initial response, (2) freedom from recurrence, and (3) quality of the subsequent cosmetic appearance (scored as good, fair, or poor). No lesion progressed and all eventually regressed completely. Cosmetic results generally were considered good by both the patient and the referring dermatologist; none of the results was considered poor. Our results demonstrate that radiation is an effective means of treating keratoacanthomas. 