Photodynamic therapy refers to a new form of phototherapy in which non-psoralen photosensitizing drugs are administered systemically or topically to an individual. The drugs alone are inactive, but once activated by high-intensity light usually from a laser, they are exceptionally effective at inhibiting the growth of hyperproliferative tissues. PDT was originally designed for the treatment of malignancies because of the unique property of several photosensitizers to localize preferentially within tumors. Porfimer sodium (Photofrin), a first generation PDT photosensitizer, has already received regulatory approval in the USA, Canada, Japan, and Europe for the management of bladder, esophageal, and lung cancers. Although PDT has not been formally approved for dermatological malignancies, its efficacy in the treatment of superficial skin cancer has been demonstrated in several clinical studies [23, 38, 43, 85, 103, 125, 151, 163, 185]. Clinical trials are currently being conducted for this indication, and approval is likely within the next few years. Because of the accessibility of the skin, there is increasing interest in using this novel form of therapy for psoriasis and other benign cutaneous disorders as well. © 2009 Springer Berlin Heidelberg.