We report a series of 10 patients who had a rapid expansion of a hypertensive intracerebral hemorrhage (HICH). It occurred in approximately 3% of 320 patients who sought treatment for HICH during the past 2 years. The site of hemorrhage was the putamen in 6 patients and the thalamus in 4 patients. Neurological deterioration occurred in a mean time of 40 hours after the onset of symptoms (range, 5.5-109 h). Fifty percent of all patients deteriorated within 24 hours. Persistent hypertension was recorded in all patients. Repeat computed tomography showed an increase of hematoma volume that was twice as large in thalamic hemorrhage and about three times as large in putaminal hemorrhage. Six patients died, whereas 3 survived with severe disability and 1 survived with moderate disability. This study indicates that continued or subsequent bleeding can occur in HICH. If those lesions are not detected early and microsurgically evacuated, they are almost always fatal. Early stereotactic evacuation with urokinase irrigation is considered more dangerous than open craniotomy by microsurgical techniques. We stress the need for attention to this problem during the acute phase of HICH.