Photodynamic therapy (PDT) is an experimental, noninvasive treatment of different malignant tumors. The principle is that applied photosensitizing substance selectively accumulate in neoplastic cells. Exposure to visible light then leads to the destruction of the tumor tissue. Following intravenous or oral administration of the photosensitizer (PS) generalised skin photosensitivity is the major side effect. Topical application of the PS under occlusive foil a novel method. Topical PDT (TPDT) is most investigated with 5-Aminolevulinic acid (ALA) as PS. ALA is a precursor of endogenous porphyrins in the biosynthetic pathway for heme. This new modality is increasingly and successfully used to treat precancerous and cancerous epithelial skin tumors, like actinic keratoses, basal-cell carcinoma, squamous-cell carcinoma and Bowen disease. An other approach of ALA-TPDT are nontumoral applications, especially psoriasis. ALA-TPDT is well tolerated by patients and makes excellent cosmetic results. It is an alternative treatment for various superficial skin tumors.