Photodynamic therapy (PDT),based on the photoactivation of photosensitizers (PSs),has become a well-studied therapy for cancer.Photofrin~,belonging to the first generation of PS,is still widely used for the treatment of different kinds of cancers;however,it has several drawbacks that significantly limit its general clinical use.Consequently,there has been extensive research on the design of PS molecules with optimized pharmaceutical properties,with aiming of overcoming the disadvantages of traditional PS,such as poor chemical purity,long half-life,excessive accumulation into the skin,and low attenuation coefficients.The rational design of novel PS with desirable properties has attracted considerable research in the pharmaceutical field.This review presents an overview on the classical photosensitizers and the most significant recent advances in the development of PS with regard to their potential application in oncology.