 Actinic keratosis AK is a skin condition that shows up on skin routinely exposed to the sun, such as the face, scalp, shoulders, chest, back, arms, and hands. The purpose of this study is to evaluate the safety of one, two, or three cycles of imiquimod for the treatment of AK. The AK lesions treated can be in adjacent and nonadjacent areas of the head, torso, and extremities. The total surface area for the AK lesions must be greater than 25 cm2. The secondary objective is to evaluate the effectiveness of treatment with imiquimod in people with large surface areas of AK. 