We produced experimental renovascular arterial hypertension in 57 rhesus monkeys by modified Goldblatt's procedures. Hypertensive fundus changes were studied in detail by serial ophthalmoscopy and fluorescein fundus angiography in all animals on a long-term follow-up, and pathologically in 23 eyes. Initial evidence of hypertensive optic neuropathy was optic disc edema which developed at the median blood pressure (BP) of 190 mmHg (normal BP, 120 mmHg). On follow-up, mild to marked pallor of the optic disc developed. The optic disc changes were correlated with BP and other fundus changes. Pathogenesis of hypertensive optic neuropathy, which has been highly controversial so far, is discussed at length in the light of the findings of the present study and other recent evidence. All the available clinical and pathologic findings in the present study indicate that hypertensive optic neuropathy represents a form of anterior ischemic optic neuropathy, and that hypertensive optic neuropathy is a distinct entity. A caution is given against a precipitous reduction of BP in patients with hypertensive optic neuropathy because that may cause complete, permanent blindness.