In order to simulate the hemorrhagic detachment stage of disciform macular degeneration, we injected fresh autologous blood into the subretinal space of albino rabbits and studied these hemorrhages clinically with the ophthalmoscope and by light and electron microscopy. One hour after injection, retinal changes were minimal and limited to occasional photoreceptor edema. At one day, there was marked damage of the photoreceptor cells characterized by edema and disintegration of the photoreceptors and pyknosis of the outer nuclear layer. Some photoreceptors had been pulled off the retina by contraction or movement of the blood clot, or both. By seven days, the photoreceptor cells were almost absent. Subretinal hemorrhage in rabbits led to irreversible retinal destruction within 24 hours. We think that the mechanism of the destruction of the overlying retina consists of a combination of a diffusion barrier by the clot, mechanical damage to the outer segments by contraction of the clot, and iron toxicity.