In 205 patients with histologically evaluated glomerulonephritis, 69 patients with essential hypertension and 12 patients with renovascular hypertension, the retina was examined and evaluated by fundus photography. Changes of the retina were classified according to the recommendations of WHO: mild to severe changes of retinal arteries were termed as mild hypertensive retinopathy, and exaggerated changes, including exudates, hemorrhages and optic disc changes, as severe hypertensive retinopathy. In spite of the short duration of renal disease and the young age of the patients in many cases, retinal changes in patients with renal hypertension were significantly more severe: especially in focal segmental sclerosis and membranoproliferative glomerulonephritis was severe hypertensive retinopathy observed. Mild hypertensive retinopathy was more prevalent in essential hypertension. When renal disease progresses the retinal findings tended to deteriorate as well. Since the 24-hour blood pressure profile was comparable in most of the groups studied, it was supposed that the vulnerability of the retina and probably other vascular beds (e.g. kidneys) was increased. We conclude that the retina of these patients should be examined even in the case of relatively mild hypertension ( > 180/100 mm Hg) and early antihypertensive treatment is an important requirement.