OBJECTIVE To evaluate the killing effect of photodynamic therapy (PDT) using new photosensitizer benzoporphyrin derivative complexed with human low density lipoprotein on retinoblastoma (RB) cell line in vitro. METHODS The experiment of photodynamic killing effect on RB cell line in vitro was performed by using benzoporphyrin derivative (BPD or Verteporfin) and monochromatic light at the wavelength around 690 nm. Seven BPD concentrations (2,500 ng/ml, 1,250 ng/ml, 625 ng/ml, 312.5 ng/ml, 156.25 ng/ml, 78.125 ng/ml, 39.0625 ng/ml) and three energy densities (1.2 J/cm2, 2.4 J/cm2 and 3.6 J/cm2) were applied. The damage of the tumor cells was evaluated by MTT assay 24 hours after PDT. The changes of the ultrastructure of RB cells were observed under eleceronic microscope 4 hours after PDT. RESULTS There was a significant dose-response relationship between tumor cell damage and BPD concentration in the medium under light irradiation at the energy density of 1.2 J/cm2. At each BPD concentration, the inhibition rate increased with the rise of energy density. RB tumor cell necrosis was found widely under electronic microscope. CONCLUSIONS This study suggested that RB cells are very sensitive to the PDT induced by BPD in vitro. RB tumor cell were directly killed by photodynamic effect induced by BPD.