Complete excision is not always easy when a keratoacanthoma is large or locat ed in certain anatomic areas. An effective nonsurgical treatment would be desira ble in such cases. This was a pilot study of the effects of intralesional interf eron alfa- 2b in the treatment of rapidly growing keratoacanthomas. A total of 4 large, rapidly growing keratoacanthomas, which were located on the lower lip, neck, and cheeks of the 4 different patients, were treated with intralesional in terferon alfa- 2b injection weekly. Serial photographs were taken to observe th e course of responses. All lesions resolved completely in 5 to 7 weekswith accep table cosmetic results. Intralesional interferon alfa-2b can be a treatment mo dality of these difficult lesions. Complete excision is not always easy when a keratoacanthoma is large or locat ed in certain anatomic areas. An effective nonsurgical treatment would be desira ble in such cases. This was a pilot study of the effects of intralesional interf eron alfa-2b in the treatment of A total of 4 large, rapidly growing keratoacanthomas, which were located on the lower lip, neck, and cheeks of the 4 different patients, were treated with intralesional in terferon alfa- 2b injection weekly. Serial photographs were taken to observe th e course of responses. All lesions resolved completely in 5 to 7 weeks with acceptable cosmetic results. Intralesional interferon alfa-2b can be a treatment mo dality of these difficult lesions.