Study participants will apply 5FU daily for 6 days; MAL/PDT is administered on 7th day. PpIX will be measured in lesions using a noninvasive dosimeter. Biopsies will be taken from selected lesions, and AKs will be photographed. Participants will be asked to complete a questionnaire to document adverse events. Patients are evaluated at day 14, and months 3, 6, 9, 12, to document AK clearance and new lesion appearance.