I devised a new ophthalmodynamometer by means of which a measured force is applied to a fundus lens, while the disk vessels are viewed at the slit-lamp microscope. In my hands, the new device was superior to the Bailliart ophthalmodynamometer when tested in normal volunteers. With the fundus lens ophthalmodynamometer, the diastolic end point differed between the two eyes by a mean of 2.3%, compared to 6.4% with the Bailliart. The new device showed a better correlation with systemic diastolic blood pressure than did the Bailliart instrument. The effect of intraocular pressure on the reading with the fundus lens device was significant, although variable.