Actinic keratosis (AK) lesions should be treated because they may evolve into lesions clinically indistinguishable from those of invasive squamous cell carcinoma which require expensive therapy. Treatment options for AK include cryosurgery, curettage and excisional surgery, dermabrasion, chemical peels, laser resurfacing, 5-fluorouracil (5-FU), imiquimod, diclofenac, and tretinoin, each with advantages and limitations. Clinical trial results show that photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA) is an effective and safe treatment of nonhypertrophic AK lesions of the scalp and face. ALA-induced protoporphyrin IX may be activated by a variety of light sources. ALA incubation times of 1-hour make ALA PDT a practical procedure for the treatment of AK lesions. Clinical trials show that PDT with methyl aminolevulinate (MAOP) is also a safe and effective treatment of AKs of the face and scalp; MAOP is available in Europe but not in the US at the time of this writing. ALA PDT offers efficacy against multiple AKs without the adverse effects of 5-FU or imiquimod.