Miconazole nitrate is a broad-spectrum antimycotic agent with low systemic and ocular toxicity. Since this drug does not adequately penetrate the vitreous cavity by topical, subconjunctival, or intravenous routes, we determined whether it can be given intravitreously for fungal endophthalmitis. Retinal and lens toxicity studies were carried out in 40 rabbits and three owl monkeys. Results showed that both miconazole and its vehicle produced toxic damage to the retina and crystalline lens in concentrations of 100 micrograms or greater. Concentrations of 10 to 80 micrograms caused mild to moderate retinal necrosis in some rabbit eyes. In monkey eyes, these concentrations did not cause significant histopathologic or electroretinographic changes. We believe that clinical use of this drug in doses not to exceed 40 micrograms may be justified in desperate cases of fungal endophthalmitis.