Nasopharyngeal carcinoma (NPC) is a prevalent cancer in some areas of southern Asia. To explore the potential of photodynamic therapy (PDT) for the treatment of NPC, a small molecule prodrug 5-aminolevulinic acid (ALA) and its methyl ester (MAL) mediated PDT was studied in vitro. The results showed that human NPC cells were sensitive to both ALA- and MAL-mediated PDT. However, ALA was more effective than MAL, possiblly due to a higher efficiency of ALA on producing endogenous protoporphyrin (PpIX) in NPC cells. Neither ALA nor MAL caused any significant genotoxicity. The ALA-based PDT might be a useful modality in the treatment ofNPC.