This is a study of 45 patients who underwent angiography and surgery of one or both carotid arteries (56 surgical procedures). All patients had detailed neuro-ophthalmological evaluations including determination of retinal artery pressure (RAP) and scrutiny for emboli in small vessels. Preoperatively, the absolute RAP value has a high correlation with the degree of stenosis of the ipsilateral carotid artery when that stenosis exceeds 80%. The asymmetry of RAP values is greatest when the stenosis is much more severe in one artery than in the other. Both RAP values may show an absolute decrease when the stenosis is severe bilaterally. In these patients, postoperatively there usually is not only an increase in the RAP on the side operated on but also on the side contralateral to the initial procedure. Almost without exception, RAP should be normal after carotid artery surgery. The finding of a subnormal RAP after operation demands immediate investigation.