Blink reflexes were obtained in a total of 34 different patients with cerebrovascular lesions; 28 were studied within 1 week of the ictus and 11 were eventually restudied. In 13, the latency of the first component of the reflex on the clinically involved side was significantly delayed (greater than 1.5 msec). This was an acute phenomenon that usually resolved within the first week after the ictus, correlated clinically with the severity of the hemiparesis and decrease in tone, and may be seen with lesions restricted to the pyramidal tract. The second component was absent in 1.7 of 34 patients during the early phase after stroke, and was associated with a decreased corneal response. These changes, which reflect decreased excitability of certain brainstem structures (rather than a lesion within those structures), are therefore potentially important for documenting CNS pathophysiology.