The use of phthalocyanines together with a free radical source for photodynamic therapy is described. The free radical sources cause the photodecomposition of the phthalocyanines, which can be useful for various reasons such as allowing light to penetrate to lower tissue levels that would otherwise be obscured. The nature of the phthalocyanine and the free radical source chosen can both have an influence on the rate of photodecomposition. The free radical sources can be provided along with the phthalocyanines either in free unattached form, or they can be attached to the phthalocyanines themselves.
