5-Aminolevulinic acid (ALA) is an important prodrug in topical photodynamic therapy (PDT). Its photosensitization is mediated through protoporphyrin Ⅸ (PpⅨ). The ALArelated drug development and application optimization promote a series of products and techniques that expanded the clinical applications of topical PDT. PpⅨ fluorescence visualization not only plays an important role in topical PDT, it is also useful in fluorescenceguided surgery for bladder cancer and gliomas. This review will provide an overview on some progress in ALA, ALA esters and PpⅨ applications.