Hematoporphyrin monomethyl ether, second generation of porphyrin-related photosensitizer, is characterized by its single form, high yield of singlet oxygen, high selectivity, and low toxicity, which has been widely used in the diagnosis and treatment of various tumors, including lung cancer, bladder cancer, and nevus flammeus and brain glioma. Hematoporphyrin monomethyl ether (HMME) is a novel and promising porphyrin-related photosensitizer for photodynamic therapy (PDT). HMME-PDT can induce cell deaththrough both necrosis and apoptosis in HeLa cells. ROS, such as singlet oxygen and hydroxyl radical, generated in HeLa cells play a decisive role in HMME-PDT-induced cell death.