Eye-ground-photos were taken in twenty-eight previously untreated men with mild to moderate essential hypertension. The same eye was evaluated before and after 26 weeks of double-blind treatment with Enalapril or Hydrochlorothiazide. The vascular changes were assessed by using a more elaborate and refined grading than the Keith-Wagener-Barker scale. All photos were examined by the same observer without knowledge of blood pressure, type of treatment or the order in which the photos had been taken. There were significant positive correlations between the vascular alterations in the retina in the untreated state and left ventricular wall thickness (echocardiography), minimal vascular resistance in the calf (plethysmography) and blood pressure respectively. Treatment with Enalapril decreased the reflection of the retinal arterial wall significantly and reduced the narrowing of arteries and arterio-venous crossing phenomena non-significantly. Hydrochlorothiazide did not affect any of the retinal vascular changes. It can be concluded that this relatively simple technique of evaluating eye-ground-photos with a new grading scale, when used in non-malignant hypertension, gives a useful assessment of the degree of hypertensive target organ damage in the retina as well as in other important target organs, i.e. the heart and vascular beds. In addition, Enalapril positively affects hypertensive retinopathy in contrast to Hydrochlorothiazide, reflecting what happens to structural cardiovascular changes in the rest of the body.