The cerebral perfusion pressure, as measured by ocular pneumoplethysmography (OPG-Gee), was used to evaluate the hemodynamic significance of carotid coiling in 25 patients, eight of whom had bilateral coiling. Positional studies were done with the head in the normal position and turned to the right and left. Seven of the 33 coilings (21%) were hemodynamically significant with the head in the normal position. A change in perfusion pressure when the head was turned was seen in 16 of 50 rotation studies (32%). There was a reduction in pressure in 11 instances and increase in five. In a control group of 24 subjects with normal angiograms, 18 of 48 studies (37%) showed a change in perfusion pressure with the head turned. Carotid coiling can be hemodynamically significant. Rotation of the head can compromise the carotid circulation whether coiling is present or not. OPG proved to be a simple means of evaluating the hemodynamic significance of carotid coiling and the effects of head rotation on the carotid circulation.