OBJECTIVE To explore the effect of photodynamic therapy with benzoporphyrin derivative monoacid ring A (BPD-MA) on the proliferation and apoptosis of human bladder cancer cells.METHODS Rhotosensitization of BPD-MA was activated with a red light laser (632.8 nm) delivered at 10 mw/cm2 to give a total dose of 2.4 J/cm2.Cellular proliferative activity was measured using the 3-(4,5-dimethylethiazil-2-yl)-2,5-Diph3-eyl tetrazolium bromide (MTT) assay and 3H-thymidine incorporation. Cell apoptosis was determined with flow cytometry analysis and the terminal deoxyuridine nicked-labeling (TUNEL) assay.RESULTS At 24 h post photodynamic treatment, photodynamic therapy significantly decreased cellular proliferative activity. The rate of apoptosis in BIU-87 cells 8 h after photodynamic treatment significantly increased up to 26.11± 2.59% as analyzed with flow cytometry. In situ labeling of DNA cleavage products with the terminal deoxyuridine nicked-labeling (TUNEL) assay reinforced these observations, BPD-MA-mediated photosensitization increased the number of TUNEL-positive cells compared to the controls. However, laser irradiation alone, BPD-MA alone and sham radiation did not affect cellular proliferative activity or apoptosis of the human bladder cancer BIU-87 cells.CONCLUSION Photodynamic therapy with BPD-MA significantly decreases cellular proliferative activity and enhances apoptosis. Therapy using this method might be a promising approach to treat patients with bladder cancer.