The alkaloid vincristine displays considerable toxicity, particularly for the retina. This type of retinopathy being an inflammatory disease, we measured the effects of a new hetrazepine platelet activating factor antagonist, BN 50730, on a vincristine-induced retinopathy in the rat. Retinal impairments were established by recording several parameters of the electroretinogram obtained from isolated retina. Our results indicate that 1) the increase in PIII duration induced by vincristine is significantly reduced by BN 50730 administration 2) the decrease in the amplitude of the PIII/b wave ratio caused by vincristine is partially inhibited by treatment with BN 50730. These experiments suggest that platelet activating factor is implicated in vincristine retinopathy and demonstrate the therapeutic effect of a specific antagonist of the mediator.