Purpose: To explore the toxicity of Mitomycin C (MMC) on trabecular meshwork cells. Methods: Bovine trabecular meshwork cells were cultured in vitro and exposed to MMC of different concentrations. The cellular morphology, ultrastructure, mortality and phagocytosis was studied with light microscopy, transmission electron microscopy and methods of Wright’s stain, etc.Results: It was found that the toxic effect of MMC on the cells was in a dose-dependent mode. 1 × 10-2 and 1 × 10-3mg/ml of MMC caused a large part of cells dead, 1 × 10-4 and 1 × 10-5mg/ml of the drug had remarkable killing effect on the cells. 1 × 10-5mg/ ml of MMC had still a mild toxicity, while 1 × 10-7 mg/ml of MMC had not any influence on cellular morphology, mortality, and phagocytosis, etc. The safe concentration on bovine trabecular meshwork cells was 1 × 10-7mg/ml and the LD50 was between 1 × 10-3and 1 × 10-4mg/ml.Conclusions: Refering to previous data, we conclude that conventional clinical-application of MMC might do har Purpose: To explore the toxicity of Mitomycin C (MMC) on trabecular meshwork cells. Methods: Bovine trabecular meshwork cells were cultured in vitro and exposed to MMC of different concentrations. The cellular morphology, ultrastructure, mortality and phagocytosis was studied with light microscopy, transmission electron microscopy and methods of Wright’s stain, etc. Results: It was found that the toxic effect of MMC on the cells was in a dose-dependent mode. 1 × 10-2 and 1 × 10-3 mg / ml of MMC caused a large part of cells dead, 1 x 10-4 and 1 x 10-5 mg / ml of the drug had remarkable killing effect on the cells. 1 x 10-5 mg / ml of MMC had still a mild toxicity, while 1 x 10- 7 mg / ml of MMC had not any influence on cellular morphology, mortality, and phagocytosis, etc. The safe concentration on bovine trabecular meshwork cells was 1 x 10-7 mg / ml and the LD50 was between 1 x 10-3 and 1 x 10 -4 mg / ml .Conclusions: Refering to previous data, we conclude that conventional clinical-application o f MMC might do har