Photodynamic therapy (PDT) involves the interaction between a photosensitizing agent and light, in the presence of oxygen, to produce photodamage to target tissue. While photodynamic therapy has been used since ancient times to treat dermatoses, it was not until the 1960s that porphyrin-based photosensitizers were first used for photodetection and phototherapy of malignancies. Thereafter, clinical experience accumulated slowly until the mid-1990s, when regulatory approval for PDT using porfimer sodium was granted in parts of North America, Europe, and Japan. This paper reviews recent clinical advances and discusses technological developments that may soon alter the way in which photodynamic therapy is used.