The experimental and clinical data on a new method of cancer treatment--photodestruction of tumours treated with the photosensitizing preparations--are reviewed. Particular emphasis is given to porphyrin compounds. The problems are considered dealing with accumulation of these compounds in cells and tissues, with the mechanism of photoalteration of sensitized tumours, with testing of the method on transplanted and spontaneous animal tumours as well as with the data on the phototherapy of human tumours with a hematoporphyrin-derivative used as a photosensitizer. The prospects for the method development are evaluated.