Objective To investigate the effect of tetrandrine (Tet) on experimental choroidal neovascularization and the effect of Tet on retinal structure and function. Methods Choroidal neovascularization was induced in 20 Brown Norway (BN) rats (40 eyes) by diode laser (wavelength: 810 nm; exposal time: 0.1 second; facular diameter:100 mu;m; energy: 120 mW), and the rats were divided randomly into experimental and control group with 10 rats (20 eyes) in each group. In experimental group, 0.05 ml Tet with the concentration of 3.21 mu;mol/L was injected intravitreously 0 and 3 days after laser photocoagulation; in the control group, the rats underwent an intravitreous injection with the same volume of sodium chloride solution. The incidence of CNV was evaluated by fundus fluorescein angiography (FFA) 14 days after laser photocoagulation. Five right eyes of another Five healthy BN rats underwent intravitreous injection with 0.05 ml Tet with the concentration of 3.21 mu;mol/L, and an intravitreous injection with the same volume of sodium chloride solution was performed on the left eyes. Before injection, 1 hour, and 1 day after the first injection, and 1 hour, 1 day, 7 days, 14 days after e second injection the electroretinography (ERG) was performed on these 5 rats; 14 days after the second injection, the retinae were examined by light microscopy and transmission electron microscopy. Results The incidence of CNV was 23.26% in experimental group，which was obviously lower than that in the control group (63.33%) (Plt;0.01). The ratio of amplitude of b wave of ERG in the rats undergone intravitreous injection with 3.21 mg/ml Tet didnprime;t differ much from which before the injection (Pgt;0.05). There were no structural changes of retinal tissues examined by light and electron microscopy. Conclusion Tet may inhibit choroidal neovascularization in rats; there isnprime;t any significant toxic effect of intravitreous injection with Tet on retina at the dosage of 3.21 mu;mol/L. (Chin J Ocul Fundus Dis, 2006, 22: 242-244)