Angiography and serial scans using radioactive Hg labeled chlormerodrin were performed in a group of patients with hemispheric "stokes." The "stokes" were separated on the basis of spinal fluid findings into "ischemic infarction" and "hemorrhagic infarction." Positive scans in the patients took the form of one of four patterns. One of these patterns (group 4) was previously described. Considering the total group of patients in the first 2 weeks, scans were positive only 24% of the time. Hemorrhagic lesions were more commonly associated with a positive scan than ischemic infarctions. About half of patients with an initially negative scan developed a positive scan after a period of several weeks.