Experimental renovascular malignant arterial hypertension was produced, by modified Goldblatt's procedures, in 60 rhesus monkeys, and hypertensive fundus changes were studied in detail (by serial ophthalmoscopy and fluorescein fundus angiography in all monkeys on a long-term follow-up, and pathologically in 29 eyes). In hypertensive choroidopathy, retinal pigment epithelial (RPE) lesions and serous retinal detachment (RD) were the classic ophthalmoscopic lesions, whereas fluorescein fundus angiography and histopathologic studies revealed marked abnormalities in the choroidal vascular bed, in addition to the changes in the RPE. The RPE lesions could be subdivided into initial acute focal lesions (due to focal RPE infarction), and degenerative lesions, which developed later and were progressive in nature, maximally involving the macular and peripheral regions of the fundus. The RD developed most commonly in the posterior pole and infrequently involved the peripheral retina. The choroidal vascular bed showed impaired circulation and extensive occlusive and ischemic changes. These studies revealed that hypertensive choroidopathy is as important a fundus change as hypertensive retinopathy. The pathogenesis of hypertensive choroidopathy is discussed in detail; the evidence indicates that it is due to choroidal ischemia, and that hypertensive choroidopathy and retinopathy are two independent and unrelated manifestations of renovascular malignant hypertension.