Abstract: Objective To investigate the inhibitory activity and the effective concentration of all-trans retinoic acid against the proliferation of human lens epithelial cells(HLEC)in vitro,and give a clue to the study on the prevention of posterior capsule opacification.Methods The passage cultured human lens epithelial cells were incubated at the condition of 37℃,5% CO₂ for 48 hours after counted and then exchanged with the medium contained 2,5,10,15,20μg/ml of all trans retinoic acid respectively as the tested groups,which were compared with the blank control group with normal medium.Then these passage cells were counted again after another 24 and 72 hours to analyze the inhibitory function on human lens epithelial cells by all-trans retinoic acid and found out its effective concentration as well as half inhibitory dose(ID₅₀).The inhibition of 24 hours cultured passive HLEC attachment by all-trans retinoic acid were also studied.Results There was a prominent inhibition on the proliferation of HLECs by all-trans retinoic acid:from 2μg/ml until 10μg/ml to reach its peak,the 24 hours ID₅₀ was 9.22μg/ml and the 72 hours one was 4.75μg/ml.Conclusion All-trans retinoic acid can inhibit the cultured HLEC proliferation and attachment in vitro and may become an ideal agent for the prevention of posterior capsule opacification in human.