Hematoporphyrin phototherapy of cancer is a new modality for cancer diagnosis and treatment that iscurrently undergoing clinical trials worldwide. A variety of tumors have been studied, e.g., breast (mostly recurrent skin), lung bladder, eye, head and neck, gynecological and brain. The most success to date has been with lung and the gynecological tract. Cell and animal studied are being conducted to elucidate the basic photobiological mechanisms involved, as well as the histopathological events associated with tumor destruction. Although major questions remain to be resolved, hematoporphyrin phototherapy is an exciting new therapeutic modality for the treatment of cancer, especially in sites where the unique features of lasers and fiber optics are advantageous. © 1986 Elsevier Science Publishers B.V. (Biomedical Division).