Inclusion Criteria:

Age greater than or equal to 18 years

- Have a t least 4 nonhypertrophic AK lesions on the body

- The subjects are in good health

- The subject has the willingness and the ability to understand and provide informed
consent for the use of their tissue and communicate to the investigator

Exclusion Criteria:

- Subjects who are pregnant or lactating

- Subjects with a history of cutaneous photosensitivity or porphyria, hypersensitivity
to porphyrins, or photodermatosis

- Subjects with use of photosensitizing drugs within 1 week of study start

- Subjects with use of topical medications such as corticosteroids, alpha-hydroxyacids
or retinoids 2 weeks before study entry

- Subjects with systemic steroid therapy within 4 weeks before study entry

- Subjects who received previous treatment of target AKs

- Subjects with systemic treatment with chemotherapeutic agents, masoprocol (Actinex),
immunotherapy, or retinoids within 2 months of study entry

- Subjects with prior history of hypersensitivity reactions to lidocaine

- Subjects who are unable to understand the protocol or to give informed consent