Photodynamic therapy (PDT) using 5-aminolevulinic acid (5-ALA) or its methyl ester (MAL) is a very effective method to treat actinic keratosis (AK). New developments will contribute to optimization of this treatment modality. This will partly be based on a better understanding of the nature of AKs. Since pain during treatment is a frequent side effect of PDT, new methods of alleviating pain are of high interest, especially when large areas are treated. A better understanding of the underlying mechanism of specific protoporphyrin IX (PPIX) accumulation can lead to further increase the response rates. New formulations might contribute to a wider acceptance of the treatment, for example a self-adhesive patch containing 5-ALA, promises easy handling, while maintaining high efficacy. New concepts in illumination, such as ambulatory PDT or daylight illumination might contribute to the further acceptance of this method.